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)/components/dashboard/stat-cards.tsx

@@ -67,6 +67,7 @@ export function DashboardStatCards({
           </div>
           <Progress
             value={capacity.average_cpu_usage_percent}
+            aria-label={t('clusterCapacity')}
             className='h-1.5'
           />
           <p className='text-[10px] text-muted-foreground'>
@@ -95,7 +96,7 @@ export function DashboardStatCards({
               {t('onlineOf', { total: summary.total_nodes })}
             </span>
           </div>
-          <Progress value={onlineRate} className='h-1.5' />
+          <Progress value={onlineRate} aria-label={t('nodeOverview')} className='h-1.5' />
           <p className='text-[10px] text-muted-foreground flex flex-wrap items-center gap-x-3 gap-y-1'>
             <span className='inline-flex items-center gap-1'>
               <Users className='size-3' />