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/repo/issue_dependency.go

@@ -55,9 +55,9 @@ func AddDependency(ctx *context.Context) {
 			return
 		}
 		// Can ctx.Doer read issues in the dep repo?
-		depRepoPerm, err := access_model.GetUserRepoPermission(ctx, dep.Repo, ctx.Doer)
+		depRepoPerm, err := access_model.GetDoerRepoPermission(ctx, dep.Repo, ctx.Doer)
 		if err != nil {
-			ctx.ServerError("GetUserRepoPermission", err)
+			ctx.ServerError("GetDoerRepoPermission", err)
 			return
 		}
 		if !depRepoPerm.CanReadIssuesOrPulls(dep.IsPull) {