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

client/src/components/PDF/JourneyBookPDF.tsx

@@ -19,8 +19,7 @@ function abs(url: string | null | undefined): string {
 }
 
 function pSrc(p: JourneyPhoto): string {
-  if (p.provider === 'local') return abs(`/uploads/${p.file_path}`)
-  return abs(`/api/integrations/memories/${p.provider}/assets/0/${p.asset_id}/${p.owner_id}/original`)
+  return abs(`/api/photos/${p.photo_id}/original`)
 }
 
 function fmtDate(d: string): string {