feat: shared DisplayCoordinator + optional API token

- Introduce DisplayCoordinator polling /api/display/monitors once per
  cycle and fan out to all per-display entities via CoordinatorEntity.
  Removes ~9x redundant requests per polling cycle that came from each
  binary_sensor/number/select/sensor/switch entity calling
  get_display_monitors() in its own async_update.
- Optimistic write-through via coordinator.apply_optimistic(...) keeps
  sibling entities in sync after slider/select writes without an extra
  network round-trip.
- Make CONF_TOKEN optional. The media server already supports running
  without auth (auth_enabled() returns False when api_tokens is empty),
  so the integration omits the Authorization header and ?token= query
  from REST/WS/album-art URLs when no token is configured. Server-side
  auth-enabled rejections still surface as invalid_auth in the UI.
- Bump manifest version to 0.3.2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom_components/remote_media_player/__init__.py

@@ -24,6 +24,7 @@ from .const import (
     SERVICE_EXECUTE_SCRIPT,
     SERVICE_PLAY_MEDIA_FILE,
 )
+from .display_coordinator import DisplayCoordinator
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -78,10 +79,20 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
         await client.close()
         return False
 
+    # Create the shared display coordinator BEFORE platform setup so each
+    # display platform's async_setup_entry can register against the same
+    # data source instead of polling /api/display/monitors on its own.
+    display_coordinator = DisplayCoordinator(hass, client)
+    try:
+        await display_coordinator.async_config_entry_first_refresh()
+    except Exception as err:  # noqa: BLE001 - first refresh wraps its own errors
+        _LOGGER.warning("Initial display monitor fetch failed, will retry: %s", err)
+
     # Store client in hass.data
     hass.data.setdefault(DOMAIN, {})
     hass.data[DOMAIN][entry.entry_id] = {
         "client": client,
+        "display_coordinator": display_coordinator,
     }
 
     # Register services if not already registered