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/picture_sources.py

@@ -12,6 +12,7 @@ from fastapi.responses import Response
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_picture_source_store,
     get_output_target_store,
     get_pp_template_store,
@@ -199,6 +200,7 @@ async def create_picture_source(
             description=data.description,
             tags=data.tags,
         )
+        fire_entity_event("picture_source", "created", stream.id)
         return _stream_to_response(stream)
     except HTTPException:
         raise
@@ -244,6 +246,7 @@ async def update_picture_source(
             description=data.description,
             tags=data.tags,
         )
+        fire_entity_event("picture_source", "updated", stream_id)
         return _stream_to_response(stream)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -271,6 +274,7 @@ async def delete_picture_source(
                        "Please reassign those targets before deleting.",
             )
         store.delete_stream(stream_id)
+        fire_entity_event("picture_source", "deleted", stream_id)
     except HTTPException:
         raise
     except ValueError as e: