Add HAOS-Server sync for optional centralized management (Phase 5)

Enable the HAOS integration to optionally connect to the standalone
Immich Watcher server for config sync and event reporting.

Server-side:
- New /api/sync/* endpoints: GET trackers, POST template render,
  POST event report
- API key auth via X-API-Key header (accepts JWT access tokens)

Integration-side:
- New sync.py: ServerSyncClient with graceful error handling
  (all methods return defaults on connection failure)
- Options flow: optional server_url and server_api_key fields
  with connection validation
- Coordinator: fire-and-forget event reporting to server when
  album changes are detected
- Translations: en.json and ru.json updated with new fields

The connection is fully additive -- the integration works identically
without a server URL configured. Server failures never break HA.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

custom_components/immich_album_watcher/__init__.py

@@ -18,6 +18,8 @@ from .const import (
     CONF_HUB_NAME,
     CONF_IMMICH_URL,
     CONF_SCAN_INTERVAL,
+    CONF_SERVER_API_KEY,
+    CONF_SERVER_URL,
     CONF_TELEGRAM_CACHE_TTL,
     DEFAULT_SCAN_INTERVAL,
     DEFAULT_TELEGRAM_CACHE_TTL,
@@ -98,6 +100,15 @@ async def async_setup_entry(hass: HomeAssistant, entry: ImmichConfigEntry) -> bo
     notification_queue = create_notification_queue(hass, entry.entry_id)
     await notification_queue.async_load()
 
+    # Create optional server sync client
+    server_url = entry.options.get(CONF_SERVER_URL, "")
+    server_api_key = entry.options.get(CONF_SERVER_API_KEY, "")
+    sync_client = None
+    if server_url and server_api_key:
+        from .sync import ServerSyncClient
+        sync_client = ServerSyncClient(hass, server_url, server_api_key)
+        _LOGGER.info("Server sync enabled: %s", server_url)
+
     # Store hub reference
     hass.data[DOMAIN][entry.entry_id] = {
         "hub": entry.runtime_data,
@@ -106,6 +117,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ImmichConfigEntry) -> bo
         "telegram_cache": telegram_cache,
         "telegram_asset_cache": telegram_asset_cache,
         "notification_queue": notification_queue,
+        "sync_client": sync_client,
         "quiet_hours_unsubs": {},  # keyed by "HH:MM" end time
     }
 
@@ -161,6 +173,7 @@ async def _async_setup_subentry_coordinator(
         storage=storage,
         telegram_cache=telegram_cache,
         telegram_asset_cache=telegram_asset_cache,
+        sync_client=hass.data[DOMAIN][entry.entry_id].get("sync_client"),
     )
 
     # Load persisted state before first refresh to detect changes during downtime