Fix issue label deletion with Actions tokens (#37013)

Use shared repo permission resolution for Actions task users in issue
label remove and clear paths, and add a regression test for deleting
issue labels with a Gitea Actions token.

This fixes issue label deletion when the request is authenticated with a
Gitea Actions token.
Fixes #37011 

The bug was that the delete path re-resolved repository permissions
using the normal user permission helper, which does not handle Actions
task users. As a result, `DELETE
/api/v1/repos/{owner}/{repo}/issues/{index}/labels/{id}` could return
`500` for Actions tokens even though label listing and label addition
worked.

---------

Co-authored-by: Codex <codex@openai.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

services/pull/update.go

@@ -108,7 +108,7 @@ func isUserAllowedToPushOrForcePushInRepoBranch(ctx context.Context, user *user_
 	}
 
 	// 1. check user push permission on the given repository
-	repoPerm, err := access_model.GetUserRepoPermission(ctx, repo, user)
+	repoPerm, err := access_model.GetDoerRepoPermission(ctx, repo, user)
 	if err != nil {
 		if repo_model.IsErrUnitTypeNotExist(err) {
 			return false, false, nil
@@ -166,7 +166,7 @@ func IsUserAllowedToUpdate(ctx context.Context, pull *issues_model.PullRequest,
 	// 4. if the pull creator allows maintainer to edit, we need to check whether
 	// user is a maintainer (has permission to merge into base branch) and inherit pull request poster's permission
 	if pull.AllowMaintainerEdit && (!pushAllowed || !rebaseAllowed) {
-		baseRepoPerm, err := access_model.GetUserRepoPermission(ctx, pull.BaseRepo, user)
+		baseRepoPerm, err := access_model.GetDoerRepoPermission(ctx, pull.BaseRepo, user)
 		if err != nil {
 			return false, false, err
 		}