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/page.tsx

@@ -10,18 +10,13 @@ export default function Home() {
   const [formData, setFormData] = useState(null)
 
   return (
-    <main className="min-h-screen p-4 md:p-8 flex flex-col items-center justify-center">
-      <div className="max-w-7xl w-full my-auto">
-        <div className="text-center mb-10">
-          <div className="inline-flex items-center justify-center w-20 h-20 bg-white rounded-full shadow-2xl mb-6">
-            <svg className="w-10 h-10 text-blue-600" 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>
-          </div>
-          <h1 className="text-5xl md:text-6xl font-bold text-white mb-4 drop-shadow-2xl">
+    <main className="min-h-screen p-8 md:p-12">
+      <div className="max-w-7xl mx-auto">
+        <div className="mb-8">
+          <h1 className="text-3xl font-bold tracking-tight mb-2">
             Kniha Jízd
           </h1>
-          <p className="text-xl md:text-2xl text-white/95 font-medium drop-shadow-lg">
+          <p className="text-muted-foreground">
             Automatizovaný systém pro správu knihy jízd
           </p>
         </div>