Feature/memory work (#61)

* refactor(conversation): separate service and repository layers for conversation module

- Split ConversationService and repository/UnitOfWork layers
- Service layer now only handles business logic and orchestration
- Repository layer handles all direct database operations
- UnitOfWork encapsulates transactional operations for messages
- Ensured all public methods have clear English docstrings with arguments, return values, and exceptions

* feat(memory): implement work memory endpoints and services

- Added API routes for conversation count, conversation list, messages, and detail.
- Integrated ConversationService for database queries and LLM-based summary generation.

* feat(memory): implement work memory endpoints and services

- Added API routes for conversation count, conversation list, messages, and detail.
- Integrated ConversationService for database queries and LLM-based summary generation.

* feat(workflow): fix issues causing workflow failures

if-else None value error
knowledge empty list rerank
end node output none node value
assigner input none value

* feat(memory): convert memory file creation time to timestamp and include title and first-line fields in file type

* fix(memory): fix serialization output and default value issues

* fix(workflow): fix issue with hybrid search logic in knowledge retrieval node

api/app/services/prompt_optimizer_service.py

@@ -3,9 +3,8 @@ import uuid
 from typing import Any, AsyncGenerator
 
 import json_repair
-from langchain_core.prompts import ChatPromptTemplate
-from sqlalchemy.orm import Session
 from jinja2 import Template
+from sqlalchemy.orm import Session
 
 from app.core.error_codes import BizCode
 from app.core.exceptions import BusinessException
@@ -177,11 +176,11 @@ class PromptOptimizerService:
             base_url=api_config.api_base
         ), type=ModelType(model_config.type))
         try:
-            with open('app/templates/prompt/prompt_optimizer_system.jinja2', 'r', encoding='utf-8') as f:
+            with open('app/services/prompt/prompt_optimizer_system.jinja2', 'r', encoding='utf-8') as f:
                 opt_system_prompt = f.read()
             rendered_system_message = Template(opt_system_prompt).render()
 
-            with open('app/templates/prompt/prompt_optimizer_user.jinja2', 'r', encoding='utf-8') as f:
+            with open('app/services/prompt/prompt_optimizer_user.jinja2', 'r', encoding='utf-8') as f:
                 opt_user_prompt = f.read()
         except FileNotFoundError:
             raise BusinessException(message="System prompt template not found", code=BizCode.NOT_FOUND)