Add built-in Web UI for media control and monitoring

- Add static file serving to FastAPI application
- Create responsive web interface with real-time updates
- Features:
  - Real-time status updates via WebSocket
  - Album artwork display with automatic updates
  - Playback controls (play, pause, next, previous)
  - Volume control with mute toggle
  - Seekable progress bar
  - Token authentication with localStorage persistence
  - Dark theme and responsive design
  - Auto-reconnect WebSocket support
- Update README with Web UI documentation
- Zero dependencies (vanilla HTML/CSS/JavaScript)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -4,14 +4,58 @@ A REST API server for controlling system media playback on Windows, Linux, macOS
 
 ## Features
 
+- **Built-in Web UI** for real-time media control and monitoring
 - Control any media player via system-wide media transport controls
 - Play/Pause/Stop/Next/Previous track
 - Volume control and mute
 - Seek within tracks
 - Get current track info (title, artist, album, artwork)
+- WebSocket support for real-time updates
 - Token-based authentication
 - Cross-platform support
 
+## Web UI
+
+The media server includes a built-in web interface for controlling and monitoring media playback.
+
+### Features
+
+- **Real-time status updates** via WebSocket connection
+- **Album artwork display** with automatic updates
+- **Playback controls** - Play, pause, next, previous
+- **Volume control** with mute toggle
+- **Seekable progress bar** - Click to jump to any position
+- **Connection status indicator** - Know when you're connected
+- **Token authentication** - Saved in browser localStorage
+- **Responsive design** - Works on desktop and mobile
+- **Dark theme** - Easy on the eyes
+
+### Accessing the Web UI
+
+1. Start the media server:
+   ```bash
+   python -m media_server.main
+   ```
+
+2. Open your browser and navigate to:
+   ```
+   http://localhost:8765/
+   ```
+
+3. Enter your API token when prompted (get it with `media-server --show-token`)
+
+4. Start playing media in any supported player and watch the UI update in real-time!
+
+### Remote Access
+
+To access the Web UI from other devices on your network:
+
+1. Find your computer's IP address (e.g., `192.168.1.100`)
+2. Navigate to `http://192.168.1.100:8765/` from any device on the same network
+3. Enter your API token
+
+**Security Note:** For remote access over the internet, use a reverse proxy with HTTPS (nginx, Caddy) to encrypt traffic.
+
 ## Requirements
 
 - Python 3.10+
@@ -71,13 +115,17 @@ Requires Termux and Termux:API apps from F-Droid.
    python -m media_server.main
    ```
 
-4. Test the connection:
-   ```bash
-   curl http://localhost:8765/api/health
-   ```
+4. **Open the Web UI** (recommended):
+   - Navigate to `http://localhost:8765/` in your browser
+   - Enter your API token from step 2
+   - Start playing media and control it from the web interface!
 
-5. Test with authentication:
+5. Or test via API:
    ```bash
+   # Health check (no auth required)
+   curl http://localhost:8765/api/health
+
+   # Get media status
    curl -H "Authorization: Bearer YOUR_TOKEN" http://localhost:8765/api/media/status
    ```