Replaces the old model where journey_photos was keyed per-entry with a
per-journey gallery table (one row per unique photo per journey) and a new
junction table journey_entry_photos that links gallery photos to entries.
Key changes:
- Migration 121: renames old journey_photos to journey_photos_old, creates the
new gallery table + junction table, backfills both from existing data, drops
the backup, removes synthetic 'Gallery' / '[Trip Photos]' wrapper entries
- journeyService: rewrites photo helpers (JP_SELECT/JOIN now joins via
journey_entry_photos → journey_photos → trek_photos); adds uploadGalleryPhotos,
addProviderPhotoToGallery, unlinkPhotoFromEntry, deleteGalleryPhoto; simplifies
deletePhoto and linkPhotoToEntry against the new schema; syncTripPhotos inserts
directly into the gallery instead of a wrapper entry
- journeyShareService: updates public photo and asset validation queries to join
through the gallery table instead of entry_id; getPublicJourney now returns a
dedicated gallery array alongside per-entry photos
- journey routes: adds gallery upload, provider-photo, and delete endpoints
(POST/DELETE /:id/gallery/*); adds unlink-from-entry route
(DELETE /entries/:entryId/photos/:journeyPhotoId); updates link-photo to
accept journey_photo_id with a backwards-compat photo_id alias
- types: adds GalleryPhoto interface
- client api: adds uploadGalleryPhotos, addProviderPhotosToGallery, unlinkPhoto,
deleteGalleryPhoto; updates linkPhoto param name to journeyPhotoId
- journeyStore: adds GalleryPhoto type, gallery field on JourneyDetail,
uploadGalleryPhotos / unlinkPhoto / deleteGalleryPhoto store actions
- JourneyDetailPage + tests: updated to work with the new gallery model
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