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/package.json

@@ -12,10 +12,13 @@
     "vue": "^3.4.15",
     "vue-router": "^4.2.5",
     "pinia": "^2.1.7",
-    "axios": "^1.6.5"
+    "axios": "^1.6.5",
+    "vuetify": "^3.5.0",
+    "@mdi/font": "^7.4.47"
   },
   "devDependencies": {
     "@vitejs/plugin-vue": "^5.0.3",
-    "vite": "^5.0.11"
+    "vite": "^5.0.11",
+    "vite-plugin-vuetify": "^2.0.1"
   }
 }