perf: Nginx 开启 gzip 压缩和静态资源缓存，加速首次加载

- gzip 压缩 JS/CSS/JSON 等资源（676KB→226KB）
- /assets/ 静态文件设置 1 年缓存（文件名含 hash）
- index.html 设置 no-cache 确保更新及时

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/Dockerfile

@@ -9,7 +9,7 @@ RUN npm run build
 
 FROM nginx:alpine
 COPY --from=builder /app/dist/ /usr/share/nginx/html/
-# SPA fallback: all routes to index.html
+# Nginx config: gzip + cache + SPA fallback
-RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  index index.html;\n  location / {\n    try_files $uri $uri/ /index.html;\n  }\n  location /api/ {\n    return 404;\n  }\n}\n' > /etc/nginx/conf.d/default.conf
+COPY nginx.conf /etc/nginx/conf.d/default.conf
 EXPOSE 80
 CMD ["nginx", "-g", "daemon off;"]

frontend/nginx.conf

@@ -0,0 +1,35 @@
+server {
+    listen 80;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Gzip compression
+    gzip on;
+    gzip_vary on;
+    gzip_min_length 256;
+    gzip_comp_level 6;
+    gzip_types
+        text/plain
+        text/css
+        text/javascript
+        application/javascript
+        application/json
+        application/xml
+        image/svg+xml;
+
+    # Static assets with hash in filename — long cache
+    location /assets/ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+    }
+
+    # SPA fallback
+    location / {
+        try_files $uri $uri/ /index.html;
+        add_header Cache-Control "no-cache";
+    }
+
+    location /api/ {
+        return 404;
+    }
+}