feat(core): bind request services and implement registered tasks

Wire plugin services through Bind/InjectFrom and AppContext so HTTP and
workers resolve dependencies after Apply. Register TaskHandler objects
with persisted results, and implement send_email_code, mail:send,
cleanup_inactive_users, and dispatch_bot_msg.

backend/plugins/domain/admin/handler/tasks.go

@@ -48,7 +48,7 @@ func abortTaskLogicError(c *gin.Context, err error) bool {
 // @Failure 403 {object} response.Any "无管理员权限"
 // @Router /api/v1/admin/tasks/types [get]
 func ListTaskTypes(c *gin.Context) {
-	c.JSON(http.StatusOK, response.OK(service.ListTaskTypes()))
+	c.JSON(http.StatusOK, response.OK(service.ListTaskTypes(c.Request.Context())))
 }
 
 // DispatchTask 下发任务