Add Retry button when creating a mirror-repo fails (#26228)

fixed #26156 
* Added a retry button in the frontend (only displayed when the status
is abnormal)
* After clicking Retry, the backend adds the task back to the task queue


![7UJDNM671RI})EA8~~XPL39](https://github.com/go-gitea/gitea/assets/3371163/e088fd63-5dcc-4bc6-8849-7db3086511b7)

![T83F1WL9)VGHR@MB956$VT9](https://github.com/go-gitea/gitea/assets/3371163/744425bb-dde1-4315-be2e-5c99ac3a44d4)

---------

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

routers/web/repo/migrate.go

@@ -259,6 +259,15 @@ func setMigrationContextData(ctx *context.Context, serviceType structs.GitServic
 	ctx.Data["service"] = serviceType
 }
 
+func MigrateRetryPost(ctx *context.Context) {
+	if err := task.RetryMigrateTask(ctx.Repo.Repository.ID); err != nil {
+		log.Error("Retry task failed: %v", err)
+		ctx.ServerError("task.RetryMigrateTask", err)
+		return
+	}
+	ctx.JSONOK()
+}
+
 func MigrateCancelPost(ctx *context.Context) {
 	migratingTask, err := admin_model.GetMigratingTask(ctx.Repo.Repository.ID)
 	if err != nil {

routers/web/web.go

@@ -953,7 +953,11 @@ func registerRoutes(m *web.Route) {
 				addSettingsSecretsRoutes()
 				addSettingVariablesRoutes()
 			}, actions.MustEnableActions)
-			m.Post("/migrate/cancel", repo.MigrateCancelPost) // this handler must be under "settings", otherwise this incomplete repo can't be accessed
+			// the follow handler must be under "settings", otherwise this incomplete repo can't be accessed
+			m.Group("/migrate", func() {
+				m.Post("/retry", repo.MigrateRetryPost)
+				m.Post("/cancel", repo.MigrateCancelPost)
+			})
 		}, ctxDataSet("PageIsRepoSettings", true, "LFSStartServer", setting.LFS.StartServer))
 	}, reqSignIn, context.RepoAssignment, context.UnitTypes(), reqRepoAdmin, context.RepoRef())