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>

package.json

@@ -0,0 +1,64 @@
+{
+  "name": "wxmp-backend",
+  "version": "0.1.0",
+  "description": "微信小程序后端 API（NestJS + Prisma + PostgreSQL + Redis + BullMQ + 腾讯云 COS）",
+  "private": true,
+  "license": "UNLICENSED",
+  "scripts": {
+    "build": "nest build",
+    "format": "prettier --write \"src/**/*.ts\" \"prisma/**/*.ts\" \"test/**/*.ts\"",
+    "lint": "eslint \"{src,prisma,test}/**/*.ts\" --fix",
+    "start": "node dist/main.js",
+    "start:dev": "ts-node-dev --respawn --transpile-only src/main.ts",
+    "start:debug": "nest start --debug --watch",
+    "start:prod": "node dist/main.js",
+    "prisma:generate": "prisma generate",
+    "prisma:migrate": "prisma migrate deploy",
+    "prisma:migrate:dev": "prisma migrate dev",
+    "prisma:studio": "prisma studio",
+    "prisma:seed": "ts-node prisma/seed.ts",
+    "db:up": "docker compose up -d postgres redis",
+    "db:down": "docker compose down"
+  },
+  "dependencies": {
+    "@nestjs/bullmq": "^11.0.0",
+    "@nestjs/common": "^11.0.0",
+    "@nestjs/config": "^4.0.0",
+    "@nestjs/core": "^11.0.0",
+    "@nestjs/jwt": "^11.0.0",
+    "@nestjs/passport": "^11.0.0",
+    "@nestjs/platform-express": "^11.0.0",
+    "@nestjs/swagger": "^11.0.0",
+    "@prisma/client": "^6.0.0",
+    "axios": "^1.7.0",
+    "bullmq": "^5.0.0",
+    "class-transformer": "^0.5.1",
+    "class-validator": "^0.14.1",
+    "dayjs": "^1.11.0",
+    "ioredis": "^5.4.0",
+    "joi": "^17.13.0",
+    "passport": "^0.7.0",
+    "passport-jwt": "^4.0.1",
+    "reflect-metadata": "^0.2.2",
+    "rxjs": "^7.8.1"
+  },
+  "devDependencies": {
+    "@nestjs/cli": "^11.0.0",
+    "@nestjs/schematics": "^11.0.0",
+    "@types/express": "^5.0.0",
+    "@types/node": "^22.0.0",
+    "@types/passport-jwt": "^4.0.1",
+    "eslint": "^9.0.0",
+    "prettier": "^3.3.0",
+    "prisma": "^6.0.0",
+    "ts-node": "^10.9.2",
+    "ts-node-dev": "^2.0.0",
+    "typescript": "^5.6.0"
+  },
+  "prisma": {
+    "seed": "ts-node prisma/seed.ts"
+  },
+  "engines": {
+    "node": ">=22"
+  }
+}