Fix template variable docs to match actual notifier output

Audit and fix all template variable references:
- template_vars.py: Add missing fields (album_id, old_shared,
  new_shared, latitude, longitude, owner_id, people per asset)
- _SAMPLE_CONTEXT: Use proper structured data matching
  build_asset_detail() output (id, owner_id, latitude, longitude,
  people per asset, playback_url for videos)
- i18n: Fix all variable descriptions for accuracy, add missing
  fields, mark scheduler-dependent slots as "not yet implemented"
- Variables modal: Add album_fields section for periodic_summary
- Shared _ASSET_FIELDS and _ALBUM_FIELDS dicts in template_vars.py
  to keep scheduled/memory slots DRY

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

packages/server/src/immich_watcher_server/api/template_configs.py

@@ -14,22 +14,37 @@ from ..database.models import TemplateConfig, User
 
 router = APIRouter(prefix="/api/template-configs", tags=["template-configs"])
 
-# Sample asset for template preview
+# Sample asset matching what build_asset_detail() actually returns
 _SAMPLE_ASSET = {
+    "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
     "filename": "IMG_001.jpg",
     "type": "IMAGE",
     "created_at": "2026-03-19T10:30:00",
     "owner": "Alice",
+    "owner_id": "user-uuid-1",
     "description": "Family picnic",
-    "url": "https://immich.example.com/photos/abc123",
-    "download_url": "https://immich.example.com/api/assets/abc123/original",
-    "photo_url": "https://immich.example.com/api/assets/abc123/thumbnail",
-    "playback_url": "",
+    "people": ["Alice", "Bob"],
     "is_favorite": True,
     "rating": 5,
+    "latitude": 48.8566,
+    "longitude": 2.3522,
     "city": "Paris",
     "state": "Île-de-France",
     "country": "France",
+    "url": "https://immich.example.com/photos/abc123",
+    "download_url": "https://immich.example.com/api/assets/abc123/original",
+    "photo_url": "https://immich.example.com/api/assets/abc123/thumbnail",
+}
+
+_SAMPLE_VIDEO_ASSET = {
+    **_SAMPLE_ASSET,
+    "id": "d4e5f6a7-b8c9-0123-defg-456789abcdef",
+    "filename": "VID_002.mp4",
+    "type": "VIDEO",
+    "is_favorite": False,
+    "rating": None,
+    "photo_url": None,
+    "playback_url": "https://immich.example.com/api/assets/def456/video",
 }
 
 _SAMPLE_ALBUM = {
@@ -39,23 +54,26 @@ _SAMPLE_ALBUM = {
     "shared": True,
 }
 
-# Full context covering all possible template variables
+# Full context covering ALL possible template variables from _build_event_data()
 _SAMPLE_CONTEXT = {
-    # Event variables
+    # Core event fields (always present)
+    "album_id": "b2eeeaa4-bba0-477a-a06f-5cb9e21818e8",
     "album_name": "Family Photos",
     "album_url": "https://immich.example.com/share/abc123",
+    "change_type": "assets_added",
     "added_count": 3,
     "removed_count": 1,
-    "change_type": "assets_added",
-    "people": ["Alice", "Bob"],
-    "added_assets": [_SAMPLE_ASSET, {**_SAMPLE_ASSET, "filename": "VID_002.mp4", "type": "VIDEO", "is_favorite": False, "rating": None, "playback_url": "https://immich.example.com/api/assets/def456/video"}],
+    "added_assets": [_SAMPLE_ASSET, _SAMPLE_VIDEO_ASSET],
     "removed_assets": ["asset-id-1", "asset-id-2"],
+    "people": ["Alice", "Bob"],
     "shared": True,
     "video_warning": "\n\n⚠️ Note: Videos may not be sent due to Telegram's 50 MB file size limit.",
-    # Rename variables
+    # Rename fields (always present, empty for non-rename events)
     "old_name": "Old Album",
     "new_name": "New Album",
-    # Scheduled/periodic variables
+    "old_shared": False,
+    "new_shared": True,
+    # Scheduled/periodic variables (for those templates)
     "albums": [_SAMPLE_ALBUM, {**_SAMPLE_ALBUM, "name": "Vacation 2025", "asset_count": 120}],
     "assets": [_SAMPLE_ASSET, {**_SAMPLE_ASSET, "filename": "IMG_002.jpg", "city": "London", "country": "UK"}],
     "date": "2026-03-19",