feat: 初始化微信小程序后端骨架

- NestJS + TypeScript + Prisma + PostgreSQL 工程骨架
- 微信登录安全流程：服务端 code2Session 换 openid 后签发 JWT，
  session_key 缓存于 Redis，不信任前端 openid
- 统一响应/异常处理、JWT 全局鉴权（@Public 豁免）、Swagger 文档
- Prisma 全量核心 schema（用户/分类/商品/设计清单/地址/订单/支付/上传/定制任务）+ seed
- 业务模块空壳（商品/分类/设计清单/地址/订单/支付/上传/BullMQ 队列）
- Docker 多阶段镜像 + 本地/生产 docker-compose
- docs：密钥获取指南、COS SDK 移除记录

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -0,0 +1,52 @@
+# 生产参考编排：app + postgres + redis 同机部署
+# 实际部署到腾讯云轻量应用服务器时按需调整端口/卷/资源限制
+services:
+  app:
+    build:
+      context: .
+      dockerfile: docker/Dockerfile
+    container_name: wxmp-app
+    restart: always
+    env_file: .env
+    environment:
+      NODE_ENV: production
+    ports:
+      - "3000:3000"
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+
+  postgres:
+    image: postgres:16-alpine
+    container_name: wxmp-postgres
+    restart: always
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER:-postgres}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+      POSTGRES_DB: ${POSTGRES_DB:-wxmp}
+    volumes:
+      - wxmp_pg_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-postgres}"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+
+  redis:
+    image: redis:7-alpine
+    container_name: wxmp-redis
+    restart: always
+    command: ["redis-server", "--appendonly", "yes"]
+    volumes:
+      - wxmp_redis_data:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+
+volumes:
+  wxmp_pg_data:
+  wxmp_redis_data: