Fix missing repository id when migrating release attachments (#36389)

This PR fixes missed repo_id on the migration of attachments to Gitea.
It also provides a doctor check to fix the dirty data on the database.

models/repo/release.go

@@ -93,6 +93,10 @@ func init() {
 	db.RegisterModel(new(Release))
 }
 
+// LegacyAttachmentMissingRepoIDCutoff marks the date when repo_id started to be written during uploads
+// (2026-01-16T00:00:00Z). Older rows might have repo_id=0 and should be tolerated once.
+const LegacyAttachmentMissingRepoIDCutoff timeutil.TimeStamp = 1768521600
+
 func (r *Release) LoadRepo(ctx context.Context) (err error) {
 	if r.Repo != nil {
 		return nil
@@ -186,6 +190,13 @@ func AddReleaseAttachments(ctx context.Context, releaseID int64, attachmentUUIDs
 	}
 
 	for i := range attachments {
+		if attachments[i].RepoID == 0 && attachments[i].CreatedUnix < LegacyAttachmentMissingRepoIDCutoff {
+			attachments[i].RepoID = rel.RepoID
+			if _, err = db.GetEngine(ctx).ID(attachments[i].ID).Cols("repo_id").Update(attachments[i]); err != nil {
+				return fmt.Errorf("update attachment repo_id [%d]: %w", attachments[i].ID, err)
+			}
+		}
+
 		if attachments[i].RepoID != rel.RepoID {
 			return util.NewPermissionDeniedErrorf("attachment belongs to different repository")
 		}