Add callbacks support for all media actions

- Add CallbackConfig model for callback scripts
- Add callbacks section to config for optional command execution
- Add turn_on/turn_off/toggle endpoints (callback-only)
- Add callbacks for all media actions (play, pause, stop, next, previous, volume, mute, seek)
- Update README with callbacks documentation

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

media_server/main.py

@@ -11,7 +11,7 @@ from fastapi.middleware.cors import CORSMiddleware
 
 from . import __version__
 from .config import settings, generate_default_config, get_config_dir
-from .routes import health_router, media_router, scripts_router
+from .routes import audio_router, health_router, media_router, scripts_router
 from .services import get_media_controller
 from .services.websocket_manager import ws_manager
 
@@ -64,6 +64,7 @@ def create_app() -> FastAPI:
     )
 
     # Register routers
+    app.include_router(audio_router)
     app.include_router(health_router)
     app.include_router(media_router)
     app.include_router(scripts_router)