认证页 axe a11y 审计+修复：7 处布局级真实违规全修，复扫验证 dashboard/admin/system 归零；基准 total_issues 保持 8 不变（纯质量收益）

Result: {"status":"keep","total_issues":8,"eslint_errors":0,"eslint_problems":0,"eslint_warnings":0,"golint_canonicalheader":0,"golint_errname":0,"golint_errorlint":1,"golint_exhaustive":0,"golint_forcetypeassert":0,"golint_gosec":0,"golint_intrange":0,"golint_modernize":3,"golint_nilnil":3,"golint_perfsprint":0,"golint_prealloc":0,"golint_recvcheck":1,"golint_test_testifylint":0,"golint_test_thelper":0,"golint_test_total":0,"golint_test_usetesting":0,"golint_total":8,"golint_usestdlibvars":0,"golint_vetx_total":0,"golint_wastedassign":0,"measure_s":93,"tsc_errors":0,"vitest_failed":0,"vitest_total":126}

frontend/app/(main)/admin/users/components/user-filter-bar.tsx

@@ -26,6 +26,7 @@ import { cn } from '@/lib/utils';
 
 export function UserFilterBar() {
   const t = useTranslations('admin.users');
+  const tCommon = useTranslations('common');
   const {
     total,
     loading,
@@ -223,6 +224,7 @@ export function UserFilterBar() {
           <Button
             variant='ghost'
             size='icon'
+            aria-label={tCommon('previousPage')}
             className='h-5.5 w-6 rounded-none rounded-l-md disabled:opacity-30'
             onClick={() => setPage(Math.max(1, page - 1))}
             disabled={page <= 1 || loading}
@@ -235,6 +237,7 @@ export function UserFilterBar() {
           <Button
             variant='ghost'
             size='icon'
+            aria-label={tCommon('nextPage')}
             className='h-5.5 w-6 rounded-none rounded-r-md disabled:opacity-30'
             onClick={() => setPage(Math.min(totalPages, page + 1))}
             disabled={page >= totalPages || loading}