Optimize KC processing and add reactive HAOS state updates

- Optimize KC frame processing: downsample to 160x90 with cv2.resize
  before rectangle extraction, pre-compute pixel coords, vectorize
  smoothing with numpy arrays
- Add WebSocket event stream for server state changes: processor manager
  fires events on start/stop, new /api/v1/events/ws endpoint streams
  them to connected clients
- Add HAOS EventStreamListener that triggers coordinator refresh on
  state changes for near-instant switch updates
- Reduce HAOS polling interval from 10s to 3s for fresher FPS metrics
- Fix overlay button tooltips: flatten nested JSON keys in locale files
  to match flat dot-notation lookup used by t() function

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

custom_components/wled_screen_controller/const.py

@@ -7,7 +7,7 @@ CONF_SERVER_URL = "server_url"
 CONF_API_KEY = "api_key"
 
 # Default values
-DEFAULT_SCAN_INTERVAL = 10  # seconds
+DEFAULT_SCAN_INTERVAL = 3  # seconds
 DEFAULT_TIMEOUT = 10  # seconds
 WS_RECONNECT_DELAY = 5  # seconds
 WS_MAX_RECONNECT_DELAY = 60  # seconds
@@ -19,3 +19,4 @@ TARGET_TYPE_KEY_COLORS = "key_colors"
 # Data keys stored in hass.data[DOMAIN][entry_id]
 DATA_COORDINATOR = "coordinator"
 DATA_WS_MANAGER = "ws_manager"
+DATA_EVENT_LISTENER = "event_listener"