feat(agent): 经验记忆 - 按任务相关度排序召回，并过期清理待批准记忆

召回按主题、情境和中文双字命中加权；30天未处理的待批准记忆会在记录和压缩调度时过期，成功计数写入运行态以免事件窗口截断后误拦。

backend/internal/app/cloud_agent_memory_compact.go

@@ -217,12 +217,15 @@ func (s *Service) startAgentMemoryCompactScheduler() {
 }
 
 func (s *Service) dispatchDueAgentMemoryCompacts() {
+	now := time.Now()
+	if _, err := s.repo.ExpirePendingAgentLessons("", now.Add(-cloudAgentPendingLessonTTL), now, 500); err != nil {
+		log.Printf("agent memory pending cleanup: %v", err)
+	}
 	rows, err := s.repo.ScheduledAgentMemorySettings(50)
 	if err != nil {
 		log.Printf("agent memory compact schedule: %v", err)
 		return
 	}
-	now := time.Now()
 	started := 0
 	for index := range rows {
 		setting := rows[index]