feat(notify-bridge): phase 4 - template system
Implement hybrid template system:
- Jinja2 SandboxedEnvironment renderer with error fallback
- Context builder: transforms ServiceEvent into flat template variables
- Template validator: checks variable references against provider type
- Default templates in EN/RU for all 8 event slots (Immich provider)
- Template loader reads .jinja2 files, returns slot->content dict
- Slots: assets_added/removed, collection_renamed/deleted, sharing_changed,
periodic_summary, scheduled_assets, memory_mode
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
alexei.dolgolyov
f36f070478