feat: Integrate shadcn/ui design system

- Install shadcn/ui dependencies (CVA, clsx, tailwind-merge, lucide-react)
- Install Radix UI primitives (slot, label)
- Create utility helper (lib/utils.ts with cn function)
- Update Tailwind config for shadcn/ui theme support
- Add CSS variables for theming in globals.css (Tailwind v4 syntax)
- Add shadcn/ui components: Button, Card, Input, Label
- Update JourneyForm with shadcn/ui components and icons
- Update DataPreview with shadcn/ui components and icons
- Improve UI consistency and accessibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/app/components/DataPreview.tsx

@@ -2,6 +2,9 @@
 
 import { useState } from 'react'
 import API_URL from '@/lib/api'
+import { Button } from '@/components/ui/button'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+import { Upload, BarChart3, Loader2, FileText, CheckCircle2, AlertCircle } from 'lucide-react'
 
 interface DataPreviewProps {
   data: any
@@ -53,63 +56,54 @@ export default function DataPreview({ data, loading, formData }: DataPreviewProp
   }
   if (loading) {
     return (
-      <div className="bg-white/98 backdrop-blur-lg rounded-3xl shadow-2xl border border-white/30 overflow-hidden">
-        <div className="flex flex-col items-center justify-center h-96 p-8">
-          <div className="relative">
-            <div className="animate-spin rounded-full h-20 w-20 border-4 border-blue-200"></div>
-            <div className="animate-spin rounded-full h-20 w-20 border-t-4 border-blue-600 absolute top-0"></div>
-          </div>
+      <Card className="bg-white/98 backdrop-blur-lg border-white/30">
+        <CardContent className="flex flex-col items-center justify-center h-96 p-8">
+          <Loader2 className="h-20 w-20 text-blue-600 animate-spin" />
           <p className="mt-6 text-gray-700 font-semibold text-lg">Načítání dat...</p>
-        </div>
-      </div>
+        </CardContent>
+      </Card>
     )
   }
 
   if (!data) {
     return (
-      <div className="bg-white/98 backdrop-blur-lg rounded-3xl shadow-2xl border border-white/30 overflow-hidden">
-        <div className="bg-gradient-to-r from-purple-50 to-purple-100 px-8 py-6 border-b border-purple-200">
-          <div className="flex items-center gap-4">
+      <Card className="bg-white/98 backdrop-blur-lg border-white/30">
+        <CardHeader className="bg-gradient-to-r from-purple-50 to-purple-100 border-b border-purple-200">
+          <CardTitle className="text-3xl font-bold text-gray-800 flex items-center gap-4">
             <div className="w-12 h-12 bg-gradient-to-br from-purple-500 to-purple-600 rounded-xl flex items-center justify-center shadow-lg">
-              <svg className="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z" />
-              </svg>
+              <BarChart3 className="w-7 h-7 text-white" />
             </div>
-            <h2 className="text-3xl font-bold text-gray-800">Náhled dat</h2>
+            <span>Náhled dat</span>
+          </CardTitle>
+        </CardHeader>
+        <CardContent className="p-8">
+          <div className="flex flex-col items-center justify-center py-16 text-center">
+            <div className="w-20 h-20 bg-gray-100 rounded-full flex items-center justify-center mb-4">
+              <FileText className="w-10 h-10 text-gray-400" />
+            </div>
+            <p className="text-gray-500 font-medium">
+              Vyplňte formulář a klikněte na "Vypočítat"
+            </p>
+            <p className="text-gray-400 text-sm mt-1">
+              Data se zobrazí zde
+            </p>
           </div>
-        </div>
-        <div className="p-8">
-        <div className="flex flex-col items-center justify-center py-16 text-center">
-          <div className="w-20 h-20 bg-gray-100 rounded-full flex items-center justify-center mb-4">
-            <svg className="w-10 h-10 text-gray-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z" />
-            </svg>
-          </div>
-          <p className="text-gray-500 font-medium">
-            Vyplňte formulář a klikněte na "Vypočítat"
-          </p>
-          <p className="text-gray-400 text-sm mt-1">
-            Data se zobrazí zde
-          </p>
-        </div>
-        </div>
-      </div>
+        </CardContent>
+      </Card>
     )
   }
 
   return (
-    <div className="bg-white/98 backdrop-blur-lg rounded-3xl shadow-2xl border border-white/30 overflow-hidden">
-      <div className="bg-gradient-to-r from-purple-50 to-purple-100 px-8 py-6 border-b border-purple-200">
-        <div className="flex items-center gap-4">
+    <Card className="bg-white/98 backdrop-blur-lg border-white/30">
+      <CardHeader className="bg-gradient-to-r from-purple-50 to-purple-100 border-b border-purple-200">
+        <CardTitle className="text-3xl font-bold text-gray-800 flex items-center gap-4">
           <div className="w-12 h-12 bg-gradient-to-br from-purple-500 to-purple-600 rounded-xl flex items-center justify-center shadow-lg">
-            <svg className="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z" />
-            </svg>
+            <BarChart3 className="w-7 h-7 text-white" />
           </div>
-          <h2 className="text-3xl font-bold text-gray-800">Náhled dat</h2>
-        </div>
-      </div>
-      <div className="p-8">
+          <span>Náhled dat</span>
+        </CardTitle>
+      </CardHeader>
+      <CardContent className="p-8">
 
       <div className="mb-6 grid grid-cols-2 gap-3 bg-gradient-to-br from-blue-50 to-indigo-50 p-5 rounded-xl border border-blue-100">
         <div>
@@ -165,23 +159,39 @@ export default function DataPreview({ data, loading, formData }: DataPreviewProp
 
       {formData && formData.startDate === '2025-01-01' && (
         <div className="mt-6">
-          <button
+          <Button
             onClick={handleFillToWebsite}
             disabled={filling}
-            className="w-full bg-gradient-to-r from-orange-600 to-orange-700 hover:from-orange-700 hover:to-orange-800 text-white font-bold py-4 px-6 rounded-xl shadow-lg hover:shadow-2xl transform hover:-translate-y-1 transition-all duration-200 disabled:opacity-50 disabled:cursor-not-allowed"
+            size="lg"
+            className="w-full bg-gradient-to-r from-orange-600 to-orange-700 hover:from-orange-700 hover:to-orange-800 text-lg h-12"
           >
-            <span className="flex items-center justify-center gap-3">
-              <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-8l-4-4m0 0L8 8m4-4v12" />
-              </svg>
-              <span className="text-lg">{filling ? 'Vyplňování...' : 'Vyplnit na web'}</span>
-            </span>
-          </button>
+            {filling ? (
+              <>
+                <Loader2 className="mr-2 h-5 w-5 animate-spin" />
+                Vyplňování...
+              </>
+            ) : (
+              <>
+                <Upload className="mr-2 h-5 w-5" />
+                Vyplnit na web
+              </>
+            )}
+          </Button>
 
           {fillResult && (
             <div className={`mt-4 ${fillResult.dry_run ? 'bg-blue-50 border-blue-200' : 'bg-green-50 border-green-200'} border rounded-xl p-4`}>
-              <h3 className={`font-bold ${fillResult.dry_run ? 'text-blue-900' : 'text-green-900'} mb-2`}>
-                {fillResult.dry_run ? 'Výsledek DRY RUN:' : 'Výsledek vyplňování:'}
+              <h3 className={`font-bold ${fillResult.dry_run ? 'text-blue-900' : 'text-green-900'} mb-2 flex items-center gap-2`}>
+                {fillResult.dry_run ? (
+                  <>
+                    <AlertCircle className="h-5 w-5" />
+                    Výsledek DRY RUN:
+                  </>
+                ) : (
+                  <>
+                    <CheckCircle2 className="h-5 w-5" />
+                    Výsledek vyplňování:
+                  </>
+                )}
               </h3>
               <div className={`text-sm ${fillResult.dry_run ? 'text-blue-800' : 'text-green-800'}`}>
                 <p>Měsíc: {fillResult.month}</p>
@@ -205,18 +215,23 @@ export default function DataPreview({ data, loading, formData }: DataPreviewProp
                   </>
                 )}
                 {fillResult.dry_run && (
-                  <p className="mt-2 font-semibold text-orange-700">
-                    ⚠️ DRY RUN MODE - Data nebyla odeslána na web
+                  <p className="mt-2 font-semibold text-orange-700 flex items-center gap-2">
+                    <AlertCircle className="h-4 w-4" />
+                    DRY RUN MODE - Data nebyla odeslána na web
                   </p>
                 )}
                 {!fillResult.dry_run && fillResult.updates_successful > 0 && (
-                  <p className="mt-2 font-semibold text-green-700">
-                    ✅ Data byla úspěšně vyplněna. Nyní zkontrolujte na webu a klikněte "Uzavřít měsíc" ručně.
+                  <p className="mt-2 font-semibold text-green-700 flex items-center gap-2">
+                    <CheckCircle2 className="h-4 w-4" />
+                    Data byla úspěšně vyplněna. Nyní zkontrolujte na webu a klikněte "Uzavřít měsíc" ručně.
                   </p>
                 )}
                 {!fillResult.dry_run && fillResult.errors && fillResult.errors.length > 0 && (
                   <div className="mt-2 p-2 bg-red-100 border border-red-300 rounded">
-                    <p className="font-semibold text-red-900">Chyby:</p>
+                    <p className="font-semibold text-red-900 flex items-center gap-2">
+                      <AlertCircle className="h-4 w-4" />
+                      Chyby:
+                    </p>
                     {fillResult.errors.map((err: any, idx: number) => (
                       <p key={idx} className="text-xs text-red-800">• {err.type} řádek {err.row}: {err.error}</p>
                     ))}
@@ -227,7 +242,7 @@ export default function DataPreview({ data, loading, formData }: DataPreviewProp
           )}
         </div>
       )}
-      </div>
-    </div>
+      </CardContent>
+    </Card>
   )
 }

frontend/app/components/JourneyForm.tsx

@@ -2,6 +2,11 @@
 
 import { useState } from 'react'
 import API_URL from '@/lib/api'
+import { Button } from '@/components/ui/button'
+import { Input } from '@/components/ui/input'
+import { Label } from '@/components/ui/label'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+import { Calculator, Download } from 'lucide-react'
 
 interface JourneyFormProps {
   onDataCalculated: (data: any) => void
@@ -99,130 +104,114 @@ export default function JourneyForm({ onDataCalculated, setLoading, onFormDataCh
   }
 
   return (
-    <div className="bg-white/98 backdrop-blur-lg rounded-3xl shadow-2xl overflow-hidden border border-white/30">
-      <div className="bg-gradient-to-r from-blue-50 to-blue-100 px-8 py-6 border-b border-blue-200">
-        <div className="flex items-center gap-4">
+    <Card className="bg-white/98 backdrop-blur-lg border-white/30">
+      <CardHeader className="bg-gradient-to-r from-blue-50 to-blue-100 border-b border-blue-200">
+        <CardTitle className="text-3xl font-bold text-gray-800 flex items-center gap-4">
           <div className="w-12 h-12 bg-gradient-to-br from-blue-500 to-blue-600 rounded-xl flex items-center justify-center shadow-lg">
             <svg className="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M11 5H6a2 2 0 00-2 2v11a2 2 0 002 2h11a2 2 0 002-2v-5m-1.414-9.414a2 2 0 112.828 2.828L11.828 15H9v-2.828l8.586-8.586z" />
             </svg>
           </div>
-          <h2 className="text-3xl font-bold text-gray-800">Vstupní údaje</h2>
-        </div>
-      </div>
-      <div className="p-8">
+          <span>Vstupní údaje</span>
+        </CardTitle>
+      </CardHeader>
+      <CardContent className="p-8">
 
       <form onSubmit={handleSubmit} className="space-y-5">
-        <div>
-          <label className="block text-sm font-medium text-gray-700 mb-1">
-            Uživatelské jméno
-          </label>
-          <input
+        <div className="space-y-2">
+          <Label htmlFor="username">Uživatelské jméno</Label>
+          <Input
+            id="username"
             type="text"
             required
             value={formData.username}
             onChange={(e) => setFormData({ ...formData, username: e.target.value })}
-            className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             placeholder="Zadejte uživatelské jméno"
           />
         </div>
 
-        <div>
-          <label className="block text-sm font-medium text-gray-700 mb-1">
-            Heslo
-          </label>
-          <input
+        <div className="space-y-2">
+          <Label htmlFor="password">Heslo</Label>
+          <Input
+            id="password"
             type="password"
             required
             value={formData.password}
             onChange={(e) => setFormData({ ...formData, password: e.target.value })}
-            className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             placeholder="Zadejte heslo"
           />
         </div>
 
         <div className="grid grid-cols-2 gap-4">
-          <div>
-            <label className="block text-sm font-medium text-gray-700 mb-1">
-              Datum od
-            </label>
-            <input
+          <div className="space-y-2">
+            <Label htmlFor="startDate">Datum od</Label>
+            <Input
+              id="startDate"
               type="date"
               required
               value={formData.startDate}
               onChange={(e) => setFormData({ ...formData, startDate: e.target.value })}
-              className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             />
           </div>
 
-          <div>
-            <label className="block text-sm font-medium text-gray-700 mb-1">
-              Datum do
-            </label>
-            <input
+          <div className="space-y-2">
+            <Label htmlFor="endDate">Datum do</Label>
+            <Input
+              id="endDate"
               type="date"
               required
               value={formData.endDate}
               onChange={(e) => setFormData({ ...formData, endDate: e.target.value })}
-              className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             />
           </div>
         </div>
 
         <div className="grid grid-cols-2 gap-4">
-          <div>
-            <label className="block text-sm font-medium text-gray-700 mb-1">
-              Počáteční stav [km]
-            </label>
-            <input
+          <div className="space-y-2">
+            <Label htmlFor="startKm">Počáteční stav [km]</Label>
+            <Input
+              id="startKm"
               type="number"
               required
               value={formData.startKm}
               onChange={(e) => setFormData({ ...formData, startKm: e.target.value })}
-              className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             />
           </div>
 
-          <div>
-            <label className="block text-sm font-medium text-gray-700 mb-1">
-              Koncový stav [km]
-            </label>
-            <input
+          <div className="space-y-2">
+            <Label htmlFor="endKm">Koncový stav [km]</Label>
+            <Input
+              id="endKm"
               type="number"
               required
               value={formData.endKm}
               onChange={(e) => setFormData({ ...formData, endKm: e.target.value })}
-              className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
             />
           </div>
         </div>
 
-        <div>
-          <label className="block text-sm font-medium text-gray-700 mb-1">
-            SPZ vozidla
-          </label>
-          <input
+        <div className="space-y-2">
+          <Label htmlFor="vehicleRegistration">SPZ vozidla</Label>
+          <Input
+            id="vehicleRegistration"
             type="text"
             value={formData.vehicleRegistration}
             onChange={(e) => setFormData({ ...formData, vehicleRegistration: e.target.value })}
-            className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
           />
         </div>
 
-        <div>
-          <label className="block text-sm font-medium text-gray-700 mb-1">
-            Variance (0-1)
-          </label>
-          <input
+        <div className="space-y-2">
+          <Label htmlFor="variance">Variance (0-1)</Label>
+          <Input
+            id="variance"
             type="number"
             step="0.01"
             min="0"
             max="1"
             value={formData.variance}
             onChange={(e) => setFormData({ ...formData, variance: e.target.value })}
-            className="w-full px-4 py-3 bg-gray-50 border border-gray-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent transition-all"
           />
-          <p className="text-xs text-gray-500 mt-1">
+          <p className="text-xs text-muted-foreground">
             Náhodná variace rozdělení kilometrů (doporučeno 0.1 = 10%)
           </p>
         </div>
@@ -237,33 +226,27 @@ export default function JourneyForm({ onDataCalculated, setLoading, onFormDataCh
         )}
 
         <div className="flex flex-col sm:flex-row gap-4 pt-6">
-          <button
+          <Button
             type="submit"
-            className="flex-1 bg-gradient-to-r from-blue-600 to-blue-700 hover:from-blue-700 hover:to-blue-800 text-white font-bold py-4 px-6 rounded-xl shadow-lg hover:shadow-2xl transform hover:-translate-y-1 transition-all duration-200"
+            size="lg"
+            className="flex-1 bg-gradient-to-r from-blue-600 to-blue-700 hover:from-blue-700 hover:to-blue-800 text-lg h-12"
           >
-            <span className="flex items-center justify-center gap-3">
-              <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 7h6m0 10v-3m-3 3h.01M9 17h.01M9 14h.01M12 14h.01M15 11h.01M12 11h.01M9 11h.01M7 21h10a2 2 0 002-2V5a2 2 0 00-2-2H7a2 2 0 00-2 2v14a2 2 0 002 2z" />
-              </svg>
-              <span className="text-lg">Vypočítat</span>
-            </span>
-          </button>
+            <Calculator className="mr-2 h-5 w-5" />
+            Vypočítat
+          </Button>
 
-          <button
+          <Button
             type="button"
             onClick={handleExport}
-            className="flex-1 bg-gradient-to-r from-green-600 to-green-700 hover:from-green-700 hover:to-green-800 text-white font-bold py-4 px-6 rounded-xl shadow-lg hover:shadow-2xl transform hover:-translate-y-1 transition-all duration-200"
+            size="lg"
+            className="flex-1 bg-gradient-to-r from-green-600 to-green-700 hover:from-green-700 hover:to-green-800 text-lg h-12"
           >
-            <span className="flex items-center justify-center gap-3">
-              <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 10v6m0 0l-3-3m3 3l3-3m2 8H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z" />
-              </svg>
-              <span className="text-lg">Export Excel</span>
-            </span>
-          </button>
+            <Download className="mr-2 h-5 w-5" />
+            Export Excel
+          </Button>
         </div>
       </form>
-      </div>
-    </div>
+      </CardContent>
+    </Card>
   )
 }