fix: 修复 docker-compose.yml 中 PostgreSQL 配置问题

问题：
- docker-compose.yml 中 DB_HOST 被硬编码为 'ai-postgres'，导致无法连接到远程 PostgreSQL 服务器
- 其他数据库配置也被硬编码，没有使用 .env 文件中的配置

修复：
- 将所有 PostgreSQL 配置改为从 .env 文件读取
- 添加 DB_URI 环境变量传递

backend/app/agent/agent_service.py

@@ -14,6 +14,7 @@ from ..model_services.chat_services import get_all_chat_services, LocalVLLMChatP
 from app.main_graph.utils.rag_initializer import init_rag_tool
 from app.core.intent_classifier import get_intent_classifier
 from app.logger import info, warning
+from app.main_graph.state import MainGraphState, CurrentAction
 
 class AIAgentService:
     def __init__(self, checkpointer):
@@ -120,8 +121,12 @@ class AIAgentService:
             "configurable": {"thread_id": thread_id},
             "metadata": {"user_id": user_id}
         }
-        input_state = {"messages": [{"role": "user", "content": message}]}
-        context = GraphContext(user_id=user_id)
+        input_state = {
+            "user_query": message,
+            "messages": [{"role": "user", "content": message}],
+            "user_id": user_id,
+            "current_action": CurrentAction.NONE
+        }
 
         # ========== 新增：混合路由 ==========
         intent_result = await self.intent_classifier.classify(message)
@@ -161,7 +166,6 @@ class AIAgentService:
             async for chunk in graph.astream(
                 input_state,
                 config=config,
-                context=context,
                 stream_mode=["messages", "updates", "custom"],
                 version="v2",
                 subgraphs=True

docker/docker-compose.yml

@@ -15,11 +15,12 @@ services:
       # =========================================================================
       # PostgreSQL 数据库配置
       # =========================================================================
-      - DB_HOST=ai-postgres
-      - DB_PORT=5432
-      - DB_USER=postgres
-      - DB_PASSWORD=${DB_PASSWORD:?请配置 DB_PASSWORD（本地：.env 文件 | CI/CD：Secrets）}  # ⭐ 敏感密钥配置
-      - DB_NAME=langgraph_db
+      - DB_HOST=${DB_HOST}
+      - DB_PORT=${DB_PORT}
+      - DB_USER=${DB_USER}
+      - DB_PASSWORD=${DB_PASSWORD}
+      - DB_NAME=${DB_NAME}
+      - DB_URI=${DB_URI}
 
       # =========================================================================
       # Qdrant 向量数据库配置（URL + API密钥 配对）