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/api/v1/user/repo.go

@@ -37,7 +37,7 @@ func listUserRepos(ctx *context.APIContext, u *user_model.User, private bool) {
 
 	apiRepos := make([]*api.Repository, 0, len(repos))
 	for i := range repos {
-		permission, err := access_model.GetUserRepoPermission(ctx, repos[i], ctx.Doer)
+		permission, err := access_model.GetDoerRepoPermission(ctx, repos[i], ctx.Doer)
 		if err != nil {
 			ctx.APIErrorInternal(err)
 			return
@@ -123,7 +123,7 @@ func ListMyRepos(ctx *context.APIContext) {
 			ctx.APIErrorInternal(err)
 			return
 		}
-		permission, err := access_model.GetUserRepoPermission(ctx, repo, ctx.Doer)
+		permission, err := access_model.GetDoerRepoPermission(ctx, repo, ctx.Doer)
 		if err != nil {
 			ctx.APIErrorInternal(err)
 		}