feat: unified photo provider abstraction layer (#584)

Introduce trek_photos as central photo registry. Frontend uses
/api/photos/:id/:kind instead of provider-specific URLs. Adding
a new photo provider is now backend-only work.

- New trek_photos table (migration 98) with photo_id FK in
  trip_photos and journey_photos
- Unified /api/photos/:id/thumbnail|original|info endpoint
- photoResolverService for central resolution and streaming
- ProviderPicker: add "All Photos" tab, rename tabs, fix i18n
- Localize all hardcoded strings in JourneyDetailPage (14 langs)
- Fix date formatting to use browser locale instead of hardcoded 'en'
- Journey stats as styled tile cards

server/src/types.ts

@@ -339,20 +339,34 @@ export interface JourneyEntry {
   updated_at: number;
 }
 
-export interface JourneyPhoto {
+export interface TrekPhoto {
   id: number;
-  entry_id: number;
-  provider: 'local' | 'immich' | 'synologyphotos';
+  provider: string;
   asset_id?: string | null;
   owner_id?: number | null;
   file_path?: string | null;
   thumbnail_path?: string | null;
-  caption?: string | null;
-  sort_order: number;
   width?: number | null;
   height?: number | null;
+  created_at: string;
+}
+
+export interface JourneyPhoto {
+  id: number;
+  entry_id: number;
+  photo_id: number;
+  caption?: string | null;
+  sort_order: number;
   shared: number;
   created_at: number;
+  // Joined from trek_photos for API responses
+  provider?: string;
+  asset_id?: string | null;
+  owner_id?: number | null;
+  file_path?: string | null;
+  thumbnail_path?: string | null;
+  width?: number | null;
+  height?: number | null;
 }
 
 export interface JourneyTrip {