fix: update backend tests and service bugs for gallery 1-to-N schema

updatePhoto: write sort_order to journey_entry_photos (junction) not journey_photos,
since JP_SELECT reads jep.sort_order — updating the gallery row had no visible effect.

deletePhoto: include id in return value so callers that check deleted.id still work.

Tests updated for new schema:
- journeyShareService: insertJourneyPhoto helper now inserts into journey_photos
  (keyed by journey_id) + journey_entry_photos junction instead of the old
  entry_id-keyed table
- SVC-081: deleteEntry cascades junction rows (journey_entry_photos), not gallery
  rows (journey_photos); assert junction is gone, gallery is preserved
- SVC-086: syncTripPhotos now populates the gallery directly — no [Trip Photos]
  wrapper entry; assert journey_photos gallery row instead
- INT-028: error message updated to 'journey_photo_id required'

server/tests/integration/journey.test.ts

@@ -649,7 +649,7 @@ describe('Link photo to entry', () => {
       .send({});
 
     expect(res.status).toBe(400);
-    expect(res.body.error).toBe('photo_id required');
+    expect(res.body.error).toBe('journey_photo_id required');
   });
 });