Fix javascript error when an anonymous user visiting migration page (#32144) (#32179)

backport #32144

This PR fixes javascript errors when an anonymous user visits the
migration page.
It also makes task view checking more restrictive.

The router moved from `/user/task/{id}/status` to
`/username/reponame/-/migrate/status` because it's a migrate status.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/web.go

@@ -667,7 +667,6 @@ func registerRoutes(m *web.Route) {
 		m.Get("/forgot_password", auth.ForgotPasswd)
 		m.Post("/forgot_password", auth.ForgotPasswdPost)
 		m.Post("/logout", auth.SignOut)
-		m.Get("/task/{task}", reqSignIn, user.TaskStatus)
 		m.Get("/stopwatches", reqSignIn, user.GetStopwatches)
 		m.Get("/search", ignExploreSignIn, user.Search)
 		m.Group("/oauth2", func() {
@@ -1036,6 +1035,13 @@ func registerRoutes(m *web.Route) {
 	}, ignSignIn, context.UserAssignmentWeb(), context.OrgAssignment())
 	// end "/{username}/-": packages, projects, code
 
+	m.Group("/{username}/{reponame}/-", func() {
+		m.Group("/migrate", func() {
+			m.Get("/status", repo.MigrateStatus)
+		})
+	}, ignSignIn, context.RepoAssignment, reqRepoCodeReader)
+	// end "/{username}/{reponame}/-": migrate
+
 	m.Group("/{username}/{reponame}/settings", func() {
 		m.Group("", func() {
 			m.Combo("").Get(repo_setting.Settings).