Redesign UI with Vuetify and improve configuration

Major changes:
- Full UI redesign with Vuetify 3 (dark theme, modern components)
- Sidebar navigation with gradient logo
- Redesigned player controls with Material Design icons
- New room cards, track lists, and filter UI with chips
- Modern auth pages with centered cards

Configuration improvements:
- Centralized all settings in root .env file
- Removed redundant backend/.env and frontend/.env files
- Increased file upload limit to 100MB (nginx + backend)
- Added build args for Vite environment variables
- Frontend now uses relative paths (better for domain deployment)

UI Components updated:
- App.vue: v-navigation-drawer with sidebar
- MiniPlayer: v-footer with modern controls
- Queue: v-list with styled items
- RoomView: improved filters with clickable chips
- All views: Vuetify cards, buttons, text fields

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

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

frontend/nginx.conf

@@ -5,7 +5,7 @@ server {
     index index.html;
 
     # Max upload size
-    client_max_body_size 30M;
+    client_max_body_size 100M;
 
     # Gzip compression
     gzip on;
@@ -27,6 +27,9 @@ server {
         proxy_buffering off;
         proxy_cache off;
         proxy_request_buffering off;
+
+        # Max upload size for API
+        client_max_body_size 100M;
     }
 
     # WebSocket proxy