Add asset preprocessing filter and enhance asset data

Features:
- Filter unprocessed assets from events and get_assets service
  - Videos require completed transcoding (encodedVideoPath)
  - Photos require generated thumbnails (thumbhash)
- Add photo_url field for images (preview-sized thumbnail)
- Simplify asset attribute names (remove asset_ prefix)
- Prioritize user-added descriptions over EXIF descriptions

Documentation:
- Update README with new asset fields and preprocessing note
- Update services.yaml parameter descriptions

Version: 2.1.0

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

custom_components/immich_album_watcher/services.yaml

@@ -167,7 +167,7 @@ send_telegram_notification:
           mode: box
     send_large_photos_as_documents:
       name: Send Large Photos As Documents
-      description: How to handle photos exceeding Telegram's limits (10MB or 10000px dimension sum). If true, send as documents. If false, downsize to fit limits.
+      description: How to handle photos exceeding Telegram's limits (10MB or 10000px dimension sum). If true, send as documents. If false, skip oversized photos.
       required: false
       default: false
       selector: