fix: add content hash to JS bundles and fix caching strategy

JS files were output as main.js without content hash, combined with
nginx's 30-day immutable cache. Browsers would never fetch updated code.

- Add [contenthash:8] to webpack output filenames in production
- Set index.html to no-cache so browsers always check for new bundles
- Only apply immutable cache to hashed filenames (*.abcdef01.js)

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

nginx.conf

@@ -29,14 +29,23 @@ server {
         proxy_read_timeout 86400;
     }
 
-    # SPA fallback
+    # SPA fallback — index.html must not be cached
     location / {
         try_files $uri $uri/ /index.html;
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
     }
 
-    # 静态资源缓存
-    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+    # Hashed static assets — long-term cache is safe
+    location ~* \.[0-9a-f]{8}\.(js|css)$ {
         expires 30d;
         add_header Cache-Control "public, immutable";
     }
+
+    # Other static assets (images, fonts) — moderate cache
+    location ~* \.(png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+        expires 7d;
+        add_header Cache-Control "public";
+    }
 }

webpack.config.js

@@ -14,8 +14,8 @@ module.exports = (env, argv) => {
     entry: './src/index.tsx',
     output: {
       path: path.resolve(__dirname, 'dist'),
-      filename: '[name].js',
-      chunkFilename: '[name].chunk.js',
+      filename: isDev ? '[name].js' : '[name].[contenthash:8].js',
+      chunkFilename: isDev ? '[name].chunk.js' : '[name].[contenthash:8].chunk.js',
       publicPath: '/',
       clean: true,
     },