Fix periodic summary image URL parameter

Use `urls` parameter (list) instead of `image_url`. Pass empty list
when image URL is not configured.

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

Common/Immich Album Watcher/blueprint.yaml

@@ -1468,7 +1468,7 @@ action:
                           data:
                             chat_id: "{{ repeat.item }}"
                             caption: "{{ periodic_summary_formatted }}"
-                            image_url: "{{ periodic_summary_image_url }}"
+                            urls: "{{ [periodic_summary_image_url] if periodic_summary_image_url | length > 0 else [] }}"
                             disable_web_page_preview: "{{ telegram_disable_url_preview }}"
                             chat_action: "{{ telegram_chat_action }}"