refine multi-turn chat in agent (#2560)

### What problem does this PR solve?

#2484

### Type of change

- [x] Performance Improvement
- [ ] Other (please describe):

api/apps/canvas_app.py

 from flask import request, Response
 from flask_login import login_required, current_user
 from api.db.services.canvas_service import CanvasTemplateService, UserCanvasService
+from api.db.services.dialog_service import full_question
+from api.db.services.user_service import TenantService
 from api.settings import RetCode
 from api.utils import get_uuid
 from api.utils.api_utils import get_json_result, server_error_response, validate_request, get_data_error_result
         canvas = Canvas(cvs.dsl, current_user.id)
         if "message" in req:
             canvas.messages.append({"role": "user", "content": req["message"], "id": message_id})
+            if len([m for m in canvas.messages if m["role"] == "user"]) > 1:
+                ten = TenantService.get_by_user_id(current_user.id)[0]
+                req["message"] = full_question(ten["tenant_id"], ten["llm_id"], canvas.messages)
             canvas.add_user_input(req["message"])
         answer = canvas.run(stream=stream)
         print(canvas)

api/apps/llm_app.py

 @manager.route('/delete_factory', methods=['POST'])
 @login_required
 @validate_request("llm_factory")
-def delete_llm():
+def delete_factory():
     req = request.json
     TenantLLMService.filter_delete(
             [TenantLLM.tenant_id == current_user.id, TenantLLM.llm_factory == req["llm_factory"]])