refactor(i18n): 移除 chrome.i18n 国际化，统一使用中文硬编码

移除 chromeI18n 工具、_locales 翻译文件和 manifest default_locale 配置，
将所有 UI 文案改为直接硬编码中文，并更新相关测试与文档。

src/components/RouterContainer.tsx

@@ -1,7 +1,6 @@
 import { FEATURES, getEntryPointType } from '@/config/features';
 import { useRouter } from '@/providers/RouterProvider';
 import { Suspense } from 'react';
-import { useI18n } from '@/utils/chromeI18n';
 import PageErrorBoundary from '@/components/PageErrorBoundary';
 import PageSkeleton from '@/components/PageSkeleton';
 import { cn } from '@/lib/utils';
@@ -11,7 +10,6 @@ const entryPointType = getEntryPointType();
 
 export default function RouterContainer() {
   const { currentPage, isLoaded } = useRouter();
-  const { t } = useI18n('common');
 
   const animationClass =
     currentPage === 'dashboard' ? 'page-transition-dashboard' : 'page-transition-enter';
@@ -43,9 +41,9 @@ export default function RouterContainer() {
               <div className="flex h-12 w-12 items-center justify-center rounded-xl bg-destructive/10 text-destructive mb-4">
                 <AlertTriangle className="h-6 w-6" />
               </div>
-              <h3 className="text-sm font-semibold text-foreground">{t('router.notFound')}</h3>
+              <h3 className="text-sm font-semibold text-foreground">{'页面未找到'}</h3>
               <p className="text-xs text-muted-foreground mt-1 max-w-[240px]">
-                {t('router.notFoundDescription', { entryPointType })}
+                {`该功能在当前运行环境（${entryPointType}）下不可用或已被移除。`}
               </p>
             </div>
           )}