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/devices.py

@@ -12,6 +12,7 @@ from wled_controller.core.devices.led_client import (
     get_provider,
 )
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_device_store,
     get_output_target_store,
     get_processor_manager,
@@ -146,6 +147,7 @@ async def create_device(
             zone_mode=device.zone_mode,
         )
 
+        fire_entity_event("device", "created", device.id)
         return _device_to_response(device)
 
     except HTTPException:
@@ -332,6 +334,7 @@ async def update_device(
             if update_data.zone_mode is not None:
                 ds.zone_mode = update_data.zone_mode
 
+        fire_entity_event("device", "updated", device_id)
         return _device_to_response(device)
 
     except ValueError as e:
@@ -369,6 +372,7 @@ async def delete_device(
         # Delete from storage
         store.delete_device(device_id)
 
+        fire_entity_event("device", "deleted", device_id)
         logger.info(f"Deleted device {device_id}")
 
     except HTTPException: