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/routes/memories/unified.ts

@@ -55,8 +55,7 @@ router.put('/unified/trips/:tripId/photos/sharing', authenticate, async (req: Re
     const result = await setTripPhotoSharing(
         tripId,
         authReq.user.id,
-        req.body?.provider,
-        req.body?.asset_id,
+        Number(req.body?.photo_id),
         req.body?.shared,
     );
     if ('error' in result) return res.status(result.error.status).json({ error: result.error.message });
@@ -66,7 +65,7 @@ router.put('/unified/trips/:tripId/photos/sharing', authenticate, async (req: Re
 router.delete('/unified/trips/:tripId/photos', authenticate, async (req: Request, res: Response) => {
     const authReq = req as AuthRequest;
     const { tripId } = req.params;
-    const result = await removeTripPhoto(tripId, authReq.user.id, req.body?.provider, req.body?.asset_id);
+    const result = removeTripPhoto(tripId, authReq.user.id, Number(req.body?.photo_id));
     if ('error' in result) return res.status(result.error.status).json({ error: result.error.message });
     res.json({ success: true });
 });