Add master display UI with audio output management and styling

- Implement main.js for the master display functionality, including WebSocket connection, audio output management, and state handling.
- Create style.css for the master display's visual design, ensuring a cohesive look and feel with a dark theme and responsive layout.
- Integrate device management with a fallback for non-Electron environments, allowing users to select audio outputs.
- Add features for managing favorites, including toggling favorites and filtering by genre.
- Enhance user experience with a responsive favorites grid and drag-to-scroll functionality.

vite.config.js

@@ -8,6 +8,10 @@ export default defineConfig({
         port: 5173,
         proxy: {
             '/api': 'http://localhost:4173',
+            // Cover-art and other static media are served by the backend's
+            // express.static('/media') mount; the dev server has to proxy
+            // them or kiosk thumbnails 404 in `npm run dev`.
+            '/media': 'http://localhost:4173',
             '/ws': { target: 'ws://localhost:4173', ws: true }
         }
     },
@@ -18,7 +22,8 @@ export default defineConfig({
             input: {
                 kiosk: resolve(__dirname, 'web/index.html'),
                 admin: resolve(__dirname, 'web/admin/index.html'),
-                docs: resolve(__dirname, 'web/docs/index.html')
+                docs: resolve(__dirname, 'web/docs/index.html'),
+                master: resolve(__dirname, 'web/master/index.html')
             }
         }
     }