feat: Modernisation UI/UX et configuration Flutter multi-plateforme

Phase 1 - Corrections Critiques:
- Fixed memory leaks dans music_provider.dart (stream subscriptions)
- Fixed race conditions dans search_provider.dart (stale results)
- Fixed token refresh errors dans api_service.dart
- Improved error handling avec messages utilisateur
- Changed API URL to HTTPS by default

Phase 2 - Améliorations UX Desktop:
- Ajouté cursor pointers sur tous les éléments cliquables
- Implémenté hover states avec effets néon glow (200ms transitions)
- Créé skeleton loading states avec shimmer animation
- Ajouté widgets: ClickableWrapper, ErrorDisplay, SkeletonLoading
- Enhanced visual feedback pour desktop users

Phase 3 - Configuration Flutter:
- Configuré Android (Gradle 8.1.0, Kotlin 1.9.0, minSdk 21, targetSdk 34)
- Créé launcher icons cyberpunk néon (5 densités)
- Configuré Windows desktop (structure complète)
- Activé Linux desktop support
- Ajouté package équatable pour entités de domaine
- Corrigé imports (colors.dart, auth_provider.dart)
- Fixed Dio API compatibility (RequestOptions)

Documentation:
- STYLE_GUIDE.md: Guide complet (100+ pages)
- DESIGN_IMPLEMENTATION_GUIDE.md: Implémentation Flutter
- BUILD_STATUS.md: Status builds + troubleshooting
- QUICKSTART_BUILDS.md: Guide rapide
- BUILD_INDEX.md: Index documentation
- PHASE_1_CORRECTIONS.md: Corrections Phase 1
- PHASE_2_UX_IMPROVEMENTS.md: Améliorations Phase 2
- PR_REVIEW_SUMMARY.md: Revue code complète
- CODE_ANALYSIS_AND_PRIORITIES.md: Analyse code

Scripts & Builds:
- BUILD_ALL.sh: Script automatisé builds multi-plateforme
- builds/: Structure avec README par plateforme
- design-system/: Système de design complet

Backend:
- Ajouté streaming HTTP Range pour audio progressif
- Enhanced YouTube service avec métadonnées complètes
- Improved error handling et validation

Generated with [Claude Code](https://claude.com/claude-code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

frontend/lib/presentation/widgets/common/clickable_wrapper.dart

@@ -0,0 +1,54 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+/// Wrapper widget that adds click cursor to clickable elements
+/// Usage: ClickableWrapper(child: YourClickableWidget())
+class ClickableWrapper extends StatelessWidget {
+  final Widget child;
+  final VoidCallback? onTap;
+  final VoidCallback? onDoubleTap;
+  final VoidCallback? onLongPress;
+  final bool isClickable;
+
+  const ClickableWrapper({
+    super.key,
+    required this.child,
+    this.onTap,
+    this.onDoubleTap,
+    this.onLongPress,
+    this.isClickable = true,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    if (!isClickable) {
+      return child;
+    }
+
+    return MouseRegion(
+      cursor: SystemMouseCursors.click,
+      child: GestureDetector(
+        onTap: onTap,
+        onDoubleTap: onDoubleTap,
+        onLongPress: onLongPress,
+        child: child,
+      ),
+    );
+  }
+}
+
+/// Extension method to wrap any widget with click cursor
+extension ClickableWrapperExtension on Widget {
+  Widget withClickCursor({
+    VoidCallback? onTap,
+    VoidCallback? onDoubleTap,
+    VoidCallback? onLongPress,
+  }) {
+    return ClickableWrapper(
+      onTap: onTap,
+      onDoubleTap: onDoubleTap,
+      onLongPress: onLongPress,
+      child: this,
+    );
+  }
+}