feat(backend): update orchestrator endpoint

- endpoints/orchestrator.py: update orchestrator API endpoint with new features

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

@@ -2,12 +2,18 @@ from __future__ import annotations
 
 from typing import Annotated
 
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, Query, status
 from sqlalchemy.orm import Session
 
 from app.api.deps import get_db
 from app.schemas.common import ErrorResponse
-from app.schemas.orchestrator import OrchestratorRequest, OrchestratorResponse
+from app.schemas.orchestrator import (
+    ConversationDeleteResponse,
+    ConversationLookupResponse,
+    OrchestratorRequest,
+    OrchestratorResponse,
+)
+from app.services.agent_conversations import AgentConversationService
 from app.services.orchestrator import OrchestratorService
 
 router = APIRouter(prefix="/orchestrator")
@@ -31,3 +37,41 @@ def run_orchestrator(payload: OrchestratorRequest, db: DbSession) -> Orchestrato
         return OrchestratorService(db).run(payload)
     except ValueError as exc:
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(exc)) from exc
+
+
+@router.get(
+    "/conversations/latest",
+    response_model=ConversationLookupResponse,
+    summary="查询当前用户最近会话",
+    description="返回当前用户最近一段可恢复的对话会话及完整消息历史。",
+)
+def get_latest_conversation(
+    user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
+    db: DbSession,
+) -> ConversationLookupResponse:
+    service = AgentConversationService(db)
+    conversation = service.get_latest_conversation_for_user(user_id=user_id, source="user_message")
+    if conversation is None:
+        return ConversationLookupResponse(found=False, conversation=None)
+
+    return ConversationLookupResponse(
+        found=True,
+        conversation=service.serialize_conversation(conversation, include_messages=True),
+    )
+
+
+@router.delete(
+    "/conversations",
+    response_model=ConversationDeleteResponse,
+    summary="删除当前用户全部会话",
+    description="删除当前用户在智能体工作台中的全部历史会话，用于显式开启全新对话。",
+)
+def delete_user_conversations(
+    user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
+    db: DbSession,
+) -> ConversationDeleteResponse:
+    deleted_count = AgentConversationService(db).delete_user_conversations(
+        user_id=user_id,
+        source="user_message",
+    )
+    return ConversationDeleteResponse(deleted_count=deleted_count)