Add entity CRUD events over WebSocket with auto-refresh

Broadcast entity_changed and device_health_changed events via the event
bus so the frontend can auto-refresh cards without polling. Adds
exponential backoff on WS reconnect.

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

server/src/wled_controller/api/routes/audio_sources.py

@@ -9,6 +9,7 @@ from starlette.websockets import WebSocket, WebSocketDisconnect
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_audio_source_store,
     get_audio_template_store,
     get_color_strip_store,
@@ -84,6 +85,7 @@ async def create_audio_source(
             audio_template_id=data.audio_template_id,
             tags=data.tags,
         )
+        fire_entity_event("audio_source", "created", source.id)
         return _to_response(source)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -123,6 +125,7 @@ async def update_audio_source(
             audio_template_id=data.audio_template_id,
             tags=data.tags,
         )
+        fire_entity_event("audio_source", "updated", source_id)
         return _to_response(source)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -146,6 +149,7 @@ async def delete_audio_source(
                 )
 
         store.delete_source(source_id)
+        fire_entity_event("audio_source", "deleted", source_id)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))