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>

routers/web/shared/user/header.go

@@ -101,7 +101,7 @@ func FindOwnerProfileReadme(ctx *context.Context, doer *user_model.User, optProf
 		return nil, nil
 	}
 
-	perm, err := access_model.GetUserRepoPermission(ctx, profileDbRepo, doer)
+	perm, err := access_model.GetDoerRepoPermission(ctx, profileDbRepo, doer)
 	if err != nil {
 		log.Error("FindOwnerProfileReadme failed to GetRepositoryByName: %v", err)
 		return nil, nil