Add non-blocking mode support to Telegram notification service

- Add `wait_for_response` parameter (default: true) for fire-and-forget operation
- Change supports_response to OPTIONAL to allow both modes
- Refactor execution logic into `_execute_telegram_notification` method
- Background tasks created with `hass.async_create_task` when wait_for_response=false
- Update documentation with non-blocking mode example and response behavior

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

custom_components/immich_album_watcher/services.yaml

@@ -109,3 +109,10 @@ send_telegram_notification:
           step: 100
           unit_of_measurement: "ms"
           mode: slider
+    wait_for_response:
+      name: Wait For Response
+      description: Wait for Telegram to finish processing before returning. Set to false for fire-and-forget (automation continues immediately).
+      required: false
+      default: true
+      selector:
+        boolean: