style: Clean minimal design matching shadcn.com aesthetic

- Remove all gradient backgrounds for clean white interface
- Update color scheme to neutral shadcn.com palette
- Simplify card headers (remove icons and colored backgrounds)
- Clean up spacing and reduce visual noise
- Update buttons to use outline variants
- Simplify table and stats styling with muted colors
- Improve typography with better font smoothing
- Match shadcn.com's minimal, professional aesthetic

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

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

frontend/app/components/JourneyForm.tsx

@@ -104,20 +104,13 @@ export default function JourneyForm({ onDataCalculated, setLoading, onFormDataCh
   }
 
   return (
-    <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>
-          <span>Vstupní údaje</span>
-        </CardTitle>
+    <Card>
+      <CardHeader>
+        <CardTitle>Vstupní údaje</CardTitle>
       </CardHeader>
-      <CardContent className="p-8">
+      <CardContent>
 
-      <form onSubmit={handleSubmit} className="space-y-5">
+      <form onSubmit={handleSubmit} className="space-y-4">
         <div className="space-y-2">
           <Label htmlFor="username">Uživatelské jméno</Label>
           <Input
@@ -225,23 +218,22 @@ export default function JourneyForm({ onDataCalculated, setLoading, onFormDataCh
           </div>
         )}
 
-        <div className="flex flex-col sm:flex-row gap-4 pt-6">
+        <div className="flex flex-col sm:flex-row gap-3 pt-4">
           <Button
             type="submit"
-            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"
+            className="flex-1"
           >
-            <Calculator className="mr-2 h-5 w-5" />
+            <Calculator className="mr-2 h-4 w-4" />
             Vypočítat
           </Button>
 
           <Button
             type="button"
             onClick={handleExport}
-            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"
+            variant="outline"
+            className="flex-1"
           >
-            <Download className="mr-2 h-5 w-5" />
+            <Download className="mr-2 h-4 w-4" />
             Export Excel
           </Button>
         </div>