feat(photos): full EXIF metadata extraction, backfill and info panel

- backend: switch EXIF parser to dsoprea/go-exif/v3 (all recognised tags, numeric normalization); store in photos.exif jsonb (migration 000003); add storage.Get and cmd/backfill-exif to backfill existing photos from S3 originals
- frontend: info panel renders all EXIF attributes with RU labels, enum translation and units (1/N, f/N, mm, EV); service tags hidden
- viewer: remove make-cover action (cover managed from panel only), icon-only download
- openspec: sync lightroom-workspace-ui artifacts (EXIF, cover-from-panel) and add plan for configurable info attributes/labels stored in user profile

backend/internal/photos/service.go

@@ -62,7 +62,7 @@ func (s *Service) Upload(ctx context.Context, in UploadInput) (*models.Photo, er
 	if !ok {
 		return nil, httpx.BadRequest("invalid_image", "could not decode image")
 	}
-	taken, lat, lon := extractEXIF(in.Data)
+	meta := extractEXIF(in.Data)
 
 	id := auth.NewID()
 	ext := strings.ToLower(filepath.Ext(in.Filename))
@@ -85,9 +85,10 @@ func (s *Service) Upload(ctx context.Context, in UploadInput) (*models.Photo, er
 		Width:            width,
 		Height:           height,
 		MimeType:         mime,
-		TakenAt:          taken,
-		Latitude:         lat,
-		Longitude:        lon,
+		TakenAt:          meta.TakenAt,
+		Latitude:         meta.Latitude,
+		Longitude:        meta.Longitude,
+		EXIF:             meta.Attributes,
 	}
 	if err := s.store.Create(ctx, p); err != nil {
 		return nil, err