Add PWA support: installable standalone app with safe area handling

- Service worker, manifest, and SVG icon for PWA installability
- Root /sw.js route for full-scope service worker registration
- Meta tags: theme-color, apple-mobile-web-app, viewport-fit=cover
- Safe area insets for notched phones (container, mini-player, footer, banner)
- Dynamic theme-color sync on light/dark toggle
- Overscroll prevention and touch-action optimization
- Hide mini-player prev/next buttons on small screens
- Updated README with PWA and new feature documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -5,7 +5,10 @@ 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
+- **Installable PWA** - Add to home screen on mobile for a native app experience
+- **Audio Visualizer** - Real-time spectrum analyzer with beat-reactive album art effects
 - **Media Browser** - Browse and play media files from configured folders
+- **Display Control** - Monitor brightness and power management
 - **Quick Actions & Scripts** - Execute custom scripts with one click
 - **Callbacks** - Trigger commands on media events (play, pause, volume, etc.)
 - Control any media player via system-wide media transport controls
@@ -36,10 +39,13 @@ The media server includes a built-in web interface for controlling and monitorin
 - **Mini player** - Sticky compact player that appears when scrolling away from the main player
 - **Connection status indicator** - Know when you're connected
 - **Token authentication** - Saved in browser localStorage
-- **Responsive design** - Works on desktop and mobile
-- **Dark and light themes** - Toggle between dark and light modes
-- **Accent color picker** - Choose from 9 preset accent colors (green, blue, purple, pink, orange, red, teal, cyan, yellow)
-- **Tab-based navigation** - Player, Browser, Quick Actions, Scripts, and Callbacks tabs
+- **Audio spectrum visualizer** - Real-time frequency bars with beat-reactive album art scaling and glow (on-demand WASAPI loopback capture)
+- **Display control** - Monitor brightness adjustment and power on/off
+- **Installable PWA** - Add to home screen on mobile/desktop for standalone app experience with safe area support for notched phones
+- **Responsive design** - Works on desktop, tablet, and mobile
+- **Dark and light themes** - Toggle between dark and light modes with dynamic status bar theming
+- **Accent color picker** - Choose from 9 preset accent colors or pick a custom color
+- **Tab-based navigation** - Player, Display, Browser, Quick Actions, and Settings tabs
 - **Multi-language support** - English and Russian locales with automatic detection
 
 ### Accessing the Web UI
@@ -58,6 +64,29 @@ The media server includes a built-in web interface for controlling and monitorin
 
 4. Start playing media in any supported player and watch the UI update in real-time!
 
+### Installing as a PWA
+
+The Web UI can be installed as a Progressive Web App for a native app-like experience:
+
+1. Open the Web UI in Chrome/Edge on your phone or desktop
+2. Tap the **Install** icon in the address bar (or "Add to Home Screen" on mobile)
+3. The app launches in standalone mode — no browser chrome, with proper safe area handling for notched phones
+
+### Audio Visualizer
+
+The Web UI includes a real-time audio spectrum visualizer that captures system audio output:
+
+- **On-demand capture** - Audio capture starts only when a client enables the visualizer, and stops when the last client disconnects
+- **Beat-reactive effects** - Album art pulses and glows in response to bass frequencies
+- **Configurable device** - Select which audio output device to capture in Settings
+
+Requires `soundcard` and `numpy` Python packages. Enable in `config.yaml`:
+
+```yaml
+visualizer_enabled: true
+# visualizer_device: "Speakers"  # optional: specific device name
+```
+
 ### Remote Access
 
 To access the Web UI from other devices on your network: