feat: add Chinese localization for Swagger UI

Replace swagger-initializer.js with custom Chinese version that
translates common UI strings and sets document title.

internal/app/middleware/swagger.go

@@ -23,6 +23,15 @@ func SwaggerHandler() gin.HandlerFunc {
 		}
 
 		isCSS := strings.HasSuffix(relPath, "swagger-ui.css")
+		isInitializer := strings.HasSuffix(relPath, "swagger-initializer.js")
+
+		if isInitializer {
+			c.Header("Content-Type", "application/javascript; charset=utf-8")
+			c.Writer.WriteHeader(200)
+			c.Writer.Write([]byte(chineseInitializer))
+			c.Request.URL.Path = rawPath
+			return
+		}
 
 		if isCSS {
 			crw := &captureResponseWriter{
@@ -83,6 +92,74 @@ func (w *captureResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 func (w *captureResponseWriter) CloseNotify() <-chan bool      { return w.ginWriter.CloseNotify() }
 func (w *captureResponseWriter) Flush()                       {}
 
+const chineseInitializer = `
+window.onload = function() {
+  window.ui = SwaggerUIBundle({
+    url: "./doc.json",
+    dom_id: '#swagger-ui',
+    deepLinking: true,
+    presets: [
+      SwaggerUIBundle.presets.apis,
+      SwaggerUIStandalonePreset
+    ],
+    plugins: [
+      SwaggerUIBundle.plugins.DownloadUrl
+    ],
+    layout: "StandaloneLayout",
+    validatorUrl: null,
+    defaultModelsExpandDepth: 1,
+    defaultModelExpandDepth: 1,
+    docExpansion: "list",
+    filter: true,
+    showExtensions: true,
+    showCommonExtensions: true,
+    withCredentials: false,
+    persistAuthorization: true,
+    tryItOutEnabled: false,
+    requestSnippetsEnabled: true,
+    displayRequestDuration: true,
+    syntaxHighlight: {
+      activate: true,
+      theme: "agate"
+    }
+  });
+
+  setTimeout(function() {
+    const translations = {
+      'Available authorizations': '可用授权',
+      'Close': '关闭',
+      'Scopes for': '作用域',
+      'Authorize': '授权',
+      'Cancel': '取消',
+      'Authorized': '已授权',
+      'Logout': '登出',
+      'Edit': '编辑',
+      'Select a definition': '选择定义',
+      'Search': '搜索',
+      'Top': '顶部',
+      'Parameters': '参数',
+      'Responses': '响应',
+      'Try it out': '试一试',
+      'Clear': '清除',
+      'Download': '下载',
+      'Show/Hide': '显示/隐藏',
+      'List Operations': '列表操作',
+      'Expand Operations': '展开操作',
+      'Models': '模型'
+    };
+
+    document.querySelectorAll('span, button, div, label').forEach(function(el) {
+      const text = el.textContent.trim();
+      if (translations[text]) {
+        el.textContent = translations[text];
+      }
+    });
+
+    document.title = 'MengStack API 文档';
+  }, 500);
+};
+`
+
 const brandingCSS = `
 /* MengStack API branding — replace Swagger SmartBear logo */
 .topbar {