feat(memory): add end user memory count filtering

- Sync memory_count after Neo4j write and forgetting cycle
- Filter Neo4j end user list by memory_count > 0
- Filter RAG end user list by Memory knowledge chunk count

api/app/schemas/end_user_schema.py

@@ -19,4 +19,6 @@ class EndUser(BaseModel):
     
     # 用户摘要和洞察更新时间
     user_summary_updated_at: Optional[datetime.datetime] = Field(description="用户摘要最后更新时间", default=None)
-    memory_insight_updated_at: Optional[datetime.datetime] = Field(description="洞察报告最后更新时间", default=None)
+    memory_insight_updated_at: Optional[datetime.datetime] = Field(description="洞察报告最后更新时间", default=None)
+    #用户记忆节点总数（Neo4j模式）
+    memory_count: int = Field(description="记忆节点总数", default=0)