feat: 添加移动端下拉菜单和主题色设置

- 新增 MobileMenu 组件，小屏幕使用汉堡菜单替代多个按钮
- 重构 LanguageSettings 为统一下拉框样式
- 新增设置页面，支持主题色切换
- 翻译页添加源语言选择器
- 更新 8 种语言的 i18n 翻译

src/design-system/base/select.tsx

@@ -31,6 +31,7 @@ const selectVariants = cva(
         default: "border-b-2 border-gray-300 bg-transparent rounded-t-md",
         bordered: "border-gray-300 bg-white",
         filled: "border-transparent bg-gray-100",
+        light: "border-transparent bg-gray-100 shadow-sm hover:bg-gray-200 font-semibold cursor-pointer",
       },
       size: {
         sm: "h-9 px-3 text-sm",
@@ -48,6 +49,11 @@ const selectVariants = cva(
         error: true,
         className: "bg-error-50",
       },
+      {
+        variant: "light",
+        error: true,
+        className: "bg-error-50 hover:bg-error-100",
+      },
     ],
     defaultVariants: {
       variant: "default",