feat (infra): Trae 完成 asset_helper_backend 微服务基础架构 V1 初始化

核心实现：搭建 Monorepo 架构，完成 shared 共享包、gateway、user-service 基础框架开发
技术落地：严格匹配指定技术栈版本，完成 Docker、gRPC、FastAPI、PostgreSQL、Redis 等配置，实现服务间基础连通
配套文件：生成 Makefile、环境变量模板、数据库 / 脚本初始化文件及启动验证文档
架构定位：仅搭建基础架构骨架，无任何业务逻辑、业务规则及业务相关字段，为后续业务开发提供支撑

asset_helper_backend/services/gateway/app/main.py

@@ -0,0 +1,42 @@
+from fastapi import FastAPI, WebSocket
+from app.api.v1 import users
+from app.ws.handlers import websocket_handler
+from app.core.config import settings
+from shared.middleware import CorrelationIdMiddleware, LoggingMiddleware, ExceptionMiddleware
+from loguru import logger
+
+app = FastAPI(
+    title="Asset Helper Gateway",
+    version="0.1.0",
+    description="Asset Helper Backend Gateway"
+)
+
+# 添加中间件
+app.add_middleware(CorrelationIdMiddleware)
+app.add_middleware(LoggingMiddleware)
+app.add_middleware(ExceptionMiddleware)
+
+# 注册路由
+app.include_router(users.router, prefix="/api/v1")
+
+# WebSocket 端点
+@app.websocket("/ws")
+async def websocket_endpoint(websocket: WebSocket):
+    await websocket_handler(websocket)
+
+@app.get("/")
+async def root():
+    return {"message": "Asset Helper Gateway is running"}
+
+@app.get("/health")
+async def health_check():
+    return {"status": "healthy"}
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run(
+        "main:app",
+        host="0.0.0.0",
+        port=settings.http_port,
+        reload=True
+    )