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/value_sources.py

@@ -8,6 +8,7 @@ from fastapi import APIRouter, Depends, HTTPException, Query, WebSocket, WebSock
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_output_target_store,
     get_processor_manager,
     get_value_source_store,
@@ -100,6 +101,7 @@ async def create_value_source(
             auto_gain=data.auto_gain,
             tags=data.tags,
         )
+        fire_entity_event("value_source", "created", source.id)
         return _to_response(source)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -150,6 +152,7 @@ async def update_value_source(
         )
         # Hot-reload running value streams
         pm.update_value_source(source_id)
+        fire_entity_event("value_source", "updated", source_id)
         return _to_response(source)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -174,6 +177,7 @@ async def delete_value_source(
                     )
 
         store.delete_source(source_id)
+        fire_entity_event("value_source", "deleted", source_id)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))