Rework create/fork/adopt/generate repository to make sure resources will be cleanup once failed (#31035)

Fix #28144 

To make the resources will be cleanup once failed. All repository
operations now follow a consistent pattern:

- 1. Create a database record for the repository with the status
being_migrated.
- 2. Register a deferred cleanup function to delete the repository and
its related data if the operation fails.
- 3.	Perform the actual Git and database operations step by step.
- 4. Upon successful completion, update the repository’s status to
ready.

The adopt operation is a special case — if it fails, the repository on
disk should not be deleted.

models/repo/release.go

@@ -558,3 +558,8 @@ func FindTagsByCommitIDs(ctx context.Context, repoID int64, commitIDs ...string)
 	}
 	return res, nil
 }
+
+func DeleteRepoReleases(ctx context.Context, repoID int64) error {
+	_, err := db.GetEngine(ctx).Where("repo_id = ?", repoID).Delete(new(Release))
+	return err
+}