feat(immich): per-album scheduled/memory dispatch + template tooling

Dispatch: honor {kind}_collection_mode on TrackingConfig — "per_collection"
fans out one event per album; "combined" pools assets as before. Extract
build_immich_dispatch_events shared by cron and test paths.

Assets: collect_scheduled_assets attaches album_name/album_url/album_public_url
to each asset so combined-mode templates can attribute rows to their source
album. Default scheduled_assets templates render a multi-album header with
inline album list and per-row album link; memory_mode follows the same pattern.

UI: "Reset to default" buttons on notification and command template slots
(per-slot and whole-template), backed by new GET /*-template-configs/defaults
endpoints. tracking-configs "Preview template" now opens an inline preview
modal with locale tabs instead of navigating away; Edit button deep-links
with ?edit_slot=<name> so the destination auto-opens the config and scrolls
to the slot. Reset confirmations use ConfirmModal instead of window.confirm.

Fixes:
* NotificationDispatcher._session_ctx infinite recursion when no shared
  aiohttp.ClientSession was passed — broke test dispatch for periodic/
  scheduled/memory (cron path was unaffected).
* telegram-bots /chats/{id}/test now resolves chat.language_override /
  language_code instead of using the raw ?locale query param, matching
  the resolution the tracker-target test endpoint already used.
* scheduled_assets default template no longer emits a blank line between
  header and the first asset when the multi-album branch is taken.

packages/server/src/notify_bridge_server/commands/immich/common.py

@@ -76,16 +76,28 @@ def build_asset_dict(
     public_url: str = "",
     year: int | None = None,
 ) -> dict[str, Any]:
-    """Build a rich asset dict for command templates from an ImmichAssetInfo or raw dict."""
+    """Build a rich asset dict for command templates from an ImmichAssetInfo or raw dict.
+
+    Asset-dict contract (shared with notification templates — see
+    ``notify_bridge_core.templates.context``): templates may read either
+    ``filename`` (the canonical field, used by notification defaults) or
+    ``originalFileName`` (the historical command-default field); both are
+    populated so a custom template authored against either key keeps working.
+    Same story for ``created_at`` / ``createdAt``.
+    """
     if isinstance(asset, dict):
         # Immich raw search responses nest geo under exifInfo — pull it out so
         # templates can use flat asset.city / asset.country.
         exif = asset.get("exifInfo") or {}
+        fname = asset.get("originalFileName") or asset.get("filename") or ""
+        created = asset.get("createdAt") or asset.get("created_at") or asset.get("fileCreatedAt") or ""
         d = {
             "id": asset.get("id", ""),
-            "originalFileName": asset.get("originalFileName", asset.get("filename", "")),
+            "filename": fname,
+            "originalFileName": fname,
             "type": asset.get("type", "IMAGE"),
-            "createdAt": asset.get("createdAt", asset.get("created_at", asset.get("fileCreatedAt", ""))),
+            "created_at": created,
+            "createdAt": created,
             "city": asset.get("city") or exif.get("city") or "",
             "country": asset.get("country") or exif.get("country") or "",
             "is_favorite": asset.get("is_favorite", asset.get("isFavorite", False)),
@@ -97,8 +109,10 @@ def build_asset_dict(
     # ImmichAssetInfo dataclass
     return {
         "id": asset.id,
+        "filename": asset.filename,
         "originalFileName": asset.filename,
         "type": asset.type,
+        "created_at": asset.created_at,
         "createdAt": asset.created_at,
         "city": getattr(asset, "city", "") or "",
         "country": getattr(asset, "country", "") or "",