feat: locale-aware notification templates + UX improvements

- Add locale support to notification templates (matching command template
  pattern): TemplateSlot now has locale field with (config_id, slot_name,
  locale) uniqueness, nested API format {slot: {locale: template}}
- Migration merges separate EN/RU system configs into unified per-provider
  configs; seeds create one config per provider with multi-locale slots
- Locale-aware dispatch with EN fallback in NotificationDispatcher
- Frontend locale tabs (EN/RU) on template config editor
- Fix tracking config cards not showing default provider icons
- Global provider filter, search palette, and various UX polish

frontend/src/routes/actions/RuleEditor.svelte

@@ -112,6 +112,7 @@
 			name: '',
 			rule_config: {
 				criteria: { person_ids: [], person_names: [], query: '', asset_type: 'all', date_from: '', date_to: '', favorite_only: false },
+				target_album_ids: [] as string[], target_album_names: [] as string[],
 				target_album_id: '', target_album_name: '',
 				create_album_if_missing: false, create_album_name: '',
 			},