feat(processed-audio-sources): phase 1 - audio filter framework

Add the foundation for audio processing filters, mirroring the existing
picture filter/postprocessing template system:
- AudioFilter base class, AudioFilterRegistry, AudioFilterOptionDef
- AudioProcessingTemplate dataclass + SQLite-backed store
- audio_filter_template meta-filter with recursive resolution
- Full REST API: CRUD templates + filter registry discovery
- Dependency injection wired in dependencies.py and main.py

server/src/wled_controller/main.py

@@ -51,6 +51,8 @@ from wled_controller.core.game_integration.community_loader import register_comm
 from wled_controller.core.mqtt.mqtt_service import MQTTService
 from wled_controller.core.mqtt.mqtt_manager import MQTTManager
 from wled_controller.storage.mqtt_source_store import MQTTSourceStore
+from wled_controller.storage.audio_processing_template_store import AudioProcessingTemplateStore
+import wled_controller.core.audio.filters  # noqa: F401 — trigger audio filter auto-registration
 from wled_controller.core.devices.mqtt_client import set_mqtt_service
 from wled_controller.core.backup.auto_backup import AutoBackupEngine
 from wled_controller.core.processing.os_notification_listener import OsNotificationListener
@@ -104,6 +106,7 @@ weather_manager = WeatherManager(weather_source_store)
 ha_store = HomeAssistantStore(db)
 ha_manager = HomeAssistantManager(ha_store)
 mqtt_source_store = MQTTSourceStore(db)
+audio_processing_template_store = AudioProcessingTemplateStore(db)
 game_integration_store = GameIntegrationStore(db)
 game_event_bus = GameEventBus()
 register_community_adapters()
@@ -231,6 +234,7 @@ async def lifespan(app: FastAPI):
         game_event_bus=game_event_bus,
         mqtt_store=mqtt_source_store,
         mqtt_manager=mqtt_manager,
+        audio_processing_template_store=audio_processing_template_store,
     )
 
     # Register devices in processor manager for health monitoring