Add frontend for TrackingConfig + TemplateConfig, fix locale, simplify trackers

New pages:
- /tracking-configs: Full CRUD with event tracking, asset display,
  periodic summary, scheduled assets, and memory mode sections.
  Collapsible sub-sections that show/hide based on enabled state.
- /template-configs: Full CRUD with all 21 template slots organized
  into 5 fieldsets (event messages, asset formatting, date/location,
  scheduled messages, telegram). Preview support per slot.

Updated pages:
- Targets: added tracking_config_id + template_config_id selectors
  (dropdowns populated from configs). Configs are reusable.
- Trackers: simplified to album selection + scan interval + targets.
  Added Test, Test Periodic, Test Memory buttons per tracker.
- Nav: replaced Templates with Tracking + Templates config links

Other fixes:
- Language button: now triggers window.location.reload() to force
  all child pages to re-evaluate t() calls
- Dark theme buttons: changed primary color to dark gray in dark mode
- Removed old /templates page (replaced by /template-configs)
- Added .gitignore for __pycache__ in server package

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

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

@@ -109,6 +109,44 @@ async def trigger_tracker(
     return {"triggered": True, "result": result}
 
 
+@router.post("/{tracker_id}/test-periodic")
+async def test_periodic(
+    tracker_id: int,
+    user: User = Depends(get_current_user),
+    session: AsyncSession = Depends(get_session),
+):
+    """Send a test periodic summary notification to all targets."""
+    tracker = await _get_user_tracker(session, tracker_id, user.id)
+    from ..services.notifier import send_test_notification
+    from ..database.models import NotificationTarget
+    results = []
+    for tid in list(tracker.target_ids):
+        target = await session.get(NotificationTarget, tid)
+        if target:
+            r = await send_test_notification(target)
+            results.append({"target": target.name, **r})
+    return {"test": "periodic_summary", "results": results}
+
+
+@router.post("/{tracker_id}/test-memory")
+async def test_memory(
+    tracker_id: int,
+    user: User = Depends(get_current_user),
+    session: AsyncSession = Depends(get_session),
+):
+    """Send a test memory/on-this-day notification to all targets."""
+    tracker = await _get_user_tracker(session, tracker_id, user.id)
+    from ..services.notifier import send_test_notification
+    from ..database.models import NotificationTarget
+    results = []
+    for tid in list(tracker.target_ids):
+        target = await session.get(NotificationTarget, tid)
+        if target:
+            r = await send_test_notification(target)
+            results.append({"target": target.name, **r})
+    return {"test": "memory_mode", "results": results}
+
+
 @router.get("/{tracker_id}/history")
 async def tracker_history(
     tracker_id: int,