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/pattern_templates.py

@@ -4,6 +4,7 @@ from fastapi import APIRouter, HTTPException, Depends
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
+    fire_entity_event,
     get_pattern_template_store,
     get_output_target_store,
 )
@@ -73,6 +74,7 @@ async def create_pattern_template(
             description=data.description,
             tags=data.tags,
         )
+        fire_entity_event("pattern_template", "created", template.id)
         return _pat_template_to_response(template)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -117,6 +119,7 @@ async def update_pattern_template(
             description=data.description,
             tags=data.tags,
         )
+        fire_entity_event("pattern_template", "updated", template_id)
         return _pat_template_to_response(template)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -143,6 +146,7 @@ async def delete_pattern_template(
                        "Please reassign those targets before deleting.",
             )
         store.delete_template(template_id)
+        fire_entity_event("pattern_template", "deleted", template_id)
     except HTTPException:
         raise
     except ValueError as e: