Replace TTL with thumbhash-based cache validation and add Telegram video size limits

- Asset cache now validates entries by comparing stored thumbhash with current
  Immich thumbhash instead of using TTL expiration. This makes cache invalidation
  precise (only when content actually changes) and eliminates unnecessary re-uploads.
  URL-based cache retains TTL for non-Immich URLs.
- Add TELEGRAM_MAX_VIDEO_SIZE (50 MB) check to skip oversized videos in both
  single-video and media-group paths, preventing entire groups from failing.
- Split media groups into sub-groups by cumulative upload size to ensure each
  sendMediaGroup request stays under Telegram's 50 MB upload limit.

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

custom_components/immich_album_watcher/__init__.py

@@ -73,11 +73,25 @@ async def async_setup_entry(hass: HomeAssistant, entry: ImmichConfigEntry) -> bo
     storage = ImmichAlbumStorage(hass, entry.entry_id)
     await storage.async_load()
 
+    # Create and load Telegram file caches once per hub (shared across all albums)
+    # TTL is in hours from config, convert to seconds
+    cache_ttl_seconds = telegram_cache_ttl * 60 * 60
+    # URL-based cache for non-Immich URLs or URLs without extractable asset IDs
+    telegram_cache = TelegramFileCache(hass, entry.entry_id, ttl_seconds=cache_ttl_seconds)
+    await telegram_cache.async_load()
+    # Asset ID-based cache for Immich URLs — uses thumbhash validation instead of TTL
+    telegram_asset_cache = TelegramFileCache(
+        hass, f"{entry.entry_id}_assets", use_thumbhash=True
+    )
+    await telegram_asset_cache.async_load()
+
     # Store hub reference
     hass.data[DOMAIN][entry.entry_id] = {
         "hub": entry.runtime_data,
         "subentries": {},
         "storage": storage,
+        "telegram_cache": telegram_cache,
+        "telegram_asset_cache": telegram_asset_cache,
     }
 
     # Track loaded subentries to detect changes
@@ -109,15 +123,11 @@ async def _async_setup_subentry_coordinator(
     album_id = subentry.data[CONF_ALBUM_ID]
     album_name = subentry.data.get(CONF_ALBUM_NAME, "Unknown Album")
     storage: ImmichAlbumStorage = hass.data[DOMAIN][entry.entry_id]["storage"]
+    telegram_cache: TelegramFileCache = hass.data[DOMAIN][entry.entry_id]["telegram_cache"]
+    telegram_asset_cache: TelegramFileCache = hass.data[DOMAIN][entry.entry_id]["telegram_asset_cache"]
 
     _LOGGER.debug("Setting up coordinator for album: %s (%s)", album_name, album_id)
 
-    # Create and load Telegram file cache for this album
-    # TTL is in hours from config, convert to seconds
-    cache_ttl_seconds = hub_data.telegram_cache_ttl * 60 * 60
-    telegram_cache = TelegramFileCache(hass, album_id, ttl_seconds=cache_ttl_seconds)
-    await telegram_cache.async_load()
-
     # Create coordinator for this album
     coordinator = ImmichAlbumWatcherCoordinator(
         hass,
@@ -129,6 +139,7 @@ async def _async_setup_subentry_coordinator(
         hub_name=hub_data.name,
         storage=storage,
         telegram_cache=telegram_cache,
+        telegram_asset_cache=telegram_asset_cache,
     )
 
     # Load persisted state before first refresh to detect changes during downtime