feat(photos): fix trash permanent delete and add empty trash

Permanently deleting a photo whose album was deleted failed because
authorization resolved through the album. Fall back to uploader
ownership when the photo is albumless. Add a bulk DELETE /trash that
removes every trashed photo the caller may delete (uncapped listing)
and returns the deleted count, with an «Очистить корзину» action on the
trash screen.

backend/internal/photos/repository.go

@@ -7,6 +7,14 @@ import (
 	"galo/internal/models"
 )
 
+// TrashIdentity is the minimal fact set needed to authorize a trashed photo
+// during a bulk purge without loading the full photo.
+type TrashIdentity struct {
+	ID         string
+	AlbumID    string
+	UploaderID string
+}
+
 // Repository is the persistence contract for the photos domain, including the
 // object ledger, variant queue and garbage collection.
 type Repository interface {
@@ -19,6 +27,9 @@ type Repository interface {
 	Clone(ctx context.Context, src *models.Photo, albumID, uploaderID, id string) error
 	HardDelete(ctx context.Context, id string) error
 	ListTrash(ctx context.Context, userID string) ([]models.Photo, error)
+	// ListTrashIdentities returns every trashed photo accessible to the user
+	// (no display cap) so a bulk purge can authorize and remove each one.
+	ListTrashIdentities(ctx context.Context, userID string) ([]TrashIdentity, error)
 	TrashCount(ctx context.Context, userID string) (int, error)
 	RestoreToAlbum(ctx context.Context, id, albumID string) error
 	AlbumExists(ctx context.Context, albumID string) (bool, error)