Replace video_warning with target_type + has_videos/has_photos

Major template system improvements:
- Remove video_warning field from TemplateConfig model
- Add target_type, has_videos, has_photos to template context
- Templates use {% if target_type == "telegram" and has_videos %}
  for conditional Telegram warnings instead of a separate field
- date_format moved from "Telegram" to "Settings" group
- Add target type selector (Telegram/Webhook) in template editor
  to preview how templates render for each target type
- All template slots now use JinjaEditor (not plain <input>)
- Preview endpoint accepts target_type parameter
- Clean up TemplateConfigCreate schema (remove stale fields)

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

packages/server/src/immich_watcher_server/database/models.py

@@ -135,9 +135,6 @@ class TemplateConfig(SQLModel, table=True):
 
     # Settings
     date_format: str = Field(default="%d.%m.%Y, %H:%M UTC")
-    video_warning: str = Field(
-        default="⚠️ Note: Videos may not be sent due to Telegram's 50 MB file size limit."
-    )
 
     created_at: datetime = Field(default_factory=_utcnow)
 
@@ -204,7 +201,9 @@ _INLINE_TEMPLATES_REMOVED = {
         '{%- if asset.is_favorite %} ❤️{% endif %}\n'
         '{%- endfor %}'
         '{%- endif %}'
-        '{%- if video_warning %}\n\n{{ video_warning }}{%- endif %}'
+        '{%- if target_type == "telegram" and has_videos %}\n\n'
+        '⚠️ Videos may not be sent due to Telegram\'s 50 MB file size limit.'
+        '{%- endif %}'
     ),
 
     "message_assets_removed": '🗑️ {{ removed_count }} photo(s) removed from album "{{ album_name }}".',
@@ -254,7 +253,9 @@ DEFAULT_TEMPLATE_RU = {
         '{%- if asset.is_favorite %} ❤️{% endif %}\n'
         '{%- endfor %}'
         '{%- endif %}'
-        '{%- if video_warning %}\n\n{{ video_warning }}{%- endif %}'
+        '{%- if target_type == "telegram" and has_videos %}\n\n'
+        '⚠️ Видео может не отправиться из-за ограничения Telegram в 50 МБ.'
+        '{%- endif %}'
     ),
 
     "message_assets_removed": '🗑️ {{ removed_count }} фото удалено из альбома "{{ album_name }}".',