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/docker-compose.yml

@@ -0,0 +1,78 @@
+version: '3.8'
+
+networks:
+  asset_helper_net:
+    driver: bridge
+
+volumes:
+  postgres_data:
+  redis_data:
+
+services:
+  postgres:
+    image: postgres:18.3-alpine3.23
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER:-admin}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-password}
+      POSTGRES_DB: ${POSTGRES_DB:-postgres}
+    ports:
+      - "5432:5432"
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U admin"]
+      interval: 30s
+      timeout: 3s
+      start_period: 5s
+      retries: 3
+    networks:
+      - asset_helper_net
+
+  redis:
+    image: redis:8.6.2-alpine
+    ports:
+      - "6379:6379"
+    volumes:
+      - redis_data:/data
+    healthcheck:
+      test: ["CMD-SHELL", "redis-cli ping"]
+      interval: 30s
+      timeout: 3s
+      start_period: 5s
+      retries: 3
+    networks:
+      - asset_helper_net
+
+  user-service:
+    build:
+      context: ./services/user-service
+    ports:
+      - "50051:50051"
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+    environment:
+      - POSTGRES_USER=${POSTGRES_USER:-admin}
+      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD:-password}
+      - REDIS_URL=${REDIS_URL:-redis://redis:6379/0}
+      - GRPC_PORT=${GRPC_PORT:-50051}
+    networks:
+      - asset_helper_net
+
+  gateway:
+    build:
+      context: ./services/gateway
+    ports:
+      - "8000:8000"
+    depends_on:
+      user-service:
+        condition: service_started
+      redis:
+        condition: service_healthy
+    environment:
+      - REDIS_URL=${REDIS_URL:-redis://redis:6379/0}
+      - HTTP_PORT=${HTTP_PORT:-8000}
+    networks:
+      - asset_helper_net