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/scene_presets.py

@@ -7,6 +7,7 @@ from fastapi import APIRouter, Depends, HTTPException
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_output_target_store,
     get_processor_manager,
     get_scene_preset_store,
@@ -87,6 +88,7 @@ async def create_scene_preset(
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
 
+    fire_entity_event("scene_preset", "created", preset.id)
     return _preset_to_response(preset)
 
 
@@ -175,6 +177,7 @@ async def update_scene_preset(
         )
     except ValueError as e:
         raise HTTPException(status_code=404 if "not found" in str(e).lower() else 400, detail=str(e))
+    fire_entity_event("scene_preset", "updated", preset_id)
     return _preset_to_response(preset)
 
 
@@ -194,6 +197,7 @@ async def delete_scene_preset(
     except ValueError as e:
         raise HTTPException(status_code=404, detail=str(e))
 
+    fire_entity_event("scene_preset", "deleted", preset_id)
 
 
 # ===== Recapture =====
@@ -259,4 +263,5 @@ async def activate_scene_preset(
     if not errors:
         logger.info(f"Scene preset '{preset.name}' activated successfully")
 
+    fire_entity_event("scene_preset", "updated", preset_id)
     return ActivateResponse(status=status, errors=errors)