feat: 添加 Docker 支持与项目文档

- 添加 Dockerfile, docker-compose.yml, .dockerignore, nginx 配置
- 添加后端 API 设计文档、平台架构需求文档、系统开发计划
- 添加 PostgreSQL schema 设计
- 更新 README.md 和 design-qa.md

docker/nginx.conf.template

@@ -0,0 +1,30 @@
+server {
+  listen 80;
+  server_name _;
+
+  root /usr/share/nginx/html;
+  index index.html;
+
+  client_max_body_size 200m;
+
+  location / {
+    try_files $uri $uri/ /index.html;
+  }
+
+  location /api {
+    proxy_pass ${API_PROXY_PASS};
+    proxy_http_version 1.1;
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_read_timeout 300s;
+    proxy_send_timeout 300s;
+  }
+
+  location ~* \.(?:js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf)$ {
+    try_files $uri =404;
+    expires 30d;
+    add_header Cache-Control "public, immutable";
+  }
+}