refactor(backend): update orchestrator endpoint and services

- endpoints/orchestrator.py: update orchestrator API endpoint
- services/agent_conversations.py: update agent conversations service
- services/orchestrator.py: update orchestrator service
- services/user_agent.py: update user agent service

server/src/app/api/v1/endpoints/orchestrator.py

@@ -48,9 +48,14 @@ def run_orchestrator(payload: OrchestratorRequest, db: DbSession) -> Orchestrato
 def get_latest_conversation(
     user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
     db: DbSession,
+    session_type: Annotated[str | None, Query(description="会话类型，例如 expense / knowledge。")] = None,
 ) -> ConversationLookupResponse:
     service = AgentConversationService(db)
-    conversation = service.get_latest_conversation_for_user(user_id=user_id, source="user_message")
+    conversation = service.get_latest_conversation_for_user(
+        user_id=user_id,
+        source="user_message",
+        session_type=session_type,
+    )
     if conversation is None:
         return ConversationLookupResponse(found=False, conversation=None)
 
@@ -60,6 +65,25 @@ def get_latest_conversation(
     )
 
 
+@router.delete(
+    "/conversations/{conversation_id}",
+    response_model=ConversationDeleteResponse,
+    summary="删除当前用户单个会话",
+    description="删除当前用户在智能体工作台中的单个会话，用于清空当前 session 内容。",
+)
+def delete_single_conversation(
+    conversation_id: str,
+    user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
+    db: DbSession,
+) -> ConversationDeleteResponse:
+    deleted_count = AgentConversationService(db).delete_conversation(
+        conversation_id=conversation_id,
+        user_id=user_id,
+        source="user_message",
+    )
+    return ConversationDeleteResponse(deleted_count=deleted_count)
+
+
 @router.delete(
     "/conversations",
     response_model=ConversationDeleteResponse,
@@ -69,9 +93,11 @@ def get_latest_conversation(
 def delete_user_conversations(
     user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
     db: DbSession,
+    session_type: Annotated[str | None, Query(description="可选，会话类型，例如 expense / knowledge。")] = None,
 ) -> ConversationDeleteResponse:
     deleted_count = AgentConversationService(db).delete_user_conversations(
         user_id=user_id,
         source="user_message",
+        session_type=session_type,
     )
     return ConversationDeleteResponse(deleted_count=deleted_count)