Add callback management API/UI and theme support

- Add callback CRUD endpoints (create, update, delete, list)
- Add callback management UI with all 11 callback events support
- Add light/dark theme switcher with localStorage persistence
- Improve button styling (wider buttons, simplified text)
- Extend ConfigManager with callback operations

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

media_server/main.py

@@ -15,7 +15,7 @@ from fastapi.staticfiles import StaticFiles
 from . import __version__
 from .auth import get_token_label, token_label_var
 from .config import settings, generate_default_config, get_config_dir
-from .routes import audio_router, health_router, media_router, scripts_router
+from .routes import audio_router, callbacks_router, health_router, media_router, scripts_router
 from .services import get_media_controller
 from .services.websocket_manager import ws_manager
 
@@ -110,6 +110,7 @@ def create_app() -> FastAPI:
 
     # Register routers
     app.include_router(audio_router)
+    app.include_router(callbacks_router)
     app.include_router(health_router)
     app.include_router(media_router)
     app.include_router(scripts_router)