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>

plans/primary-plan.md

@@ -222,6 +222,12 @@ async def _execute_telegram_notification(self, ...):
 - Natural language tracker configuration via Telegram chat
 - **Subplan**: `plans/phase-6-claude-ai-bot.md`
 
+### Phase 11: Snackbar Notifications `[ ]`
+- Unified toast/snackbar system for action feedback (success, error, info, warning)
+- Replace all `alert()` calls with typed snackbars
+- Auto-dismiss, stacking, accessible, animated
+- **Subplan**: `plans/phase-11-snackbar-notifications.md`
+
 ---
 
 ## Verification