feat(a11y): 设置页无障碍审计并修复开关可访问名称

axe 结构性规则扩展到设置页（安全 Tab + 其他 Tab）：
- security-tab 8 个 Switch/SelectTrigger 补可访问名称（Label htmlFor 关联 + aria-label）
- other-tab / auth-source-modal 各 1 个未命名 Switch 补 aria-label
- 新增 2 个 axe 测试，vitest 126 全绿
- 翻译键 loginCaptchaEnabled 加入 fragments（admin.zh-CN/en）

frontend/components/common/settings/auth-source-modal.tsx

@@ -180,6 +180,7 @@ export function AuthSourceModal({
               </div>
             </div>
             <Switch
+              aria-label={t('enableAuthSource')}
               checked={form.is_active}
               onCheckedChange={(checked) =>
                 setForm((prev) => ({ ...prev, is_active: checked }))

frontend/components/common/settings/other-tab.tsx

@@ -314,6 +314,7 @@ export function OtherTab({ configs }: OtherTabProps) {
                     </div>
                     <div className='flex items-center'>
                       <Switch
+                        aria-label={tNav(item.labelKey)}
                         checked={checked}
                         disabled={
                           isReadOnly || updateMenuConfigMutation.isPending

frontend/components/common/settings/security-tab.tsx

@@ -329,15 +329,19 @@ export function SecurityTab({ configs, systemConfigsQuery }: SecurityTabProps) {
                   <div className='space-y-1'>
                     <div className='flex items-center gap-2'>
                       {Icon && <Icon className='size-4 text-primary' />}
-                      <span className='font-medium text-sm text-foreground'>
+                      <Label
+                        htmlFor={item.key}
+                        className='font-medium text-sm text-foreground'
+                      >
                         {t(item.titleKey)}
-                      </span>
+                      </Label>
                     </div>
                     <p className='text-xs text-muted-foreground leading-relaxed pr-2'>
                       {t(item.descKey)}
                     </p>
                   </div>
                   <Switch
+                    id={item.key}
                     checked={checked}
                     disabled={updateConfigMutation.isPending}
                     onCheckedChange={(value) => handleToggle(item.key, value)}
@@ -366,7 +370,10 @@ export function SecurityTab({ configs, systemConfigsQuery }: SecurityTabProps) {
                   disabled={updateTTLMutation.isPending}
                   onValueChange={handleTTLChange}
                 >
-                  <SelectTrigger className='w-[180px] bg-card border-dashed text-xs h-8'>
+                  <SelectTrigger
+                    className='w-[180px] bg-card border-dashed text-xs h-8'
+                    aria-label={t('loginSessionTTL')}
+                  >
                     <SelectValue placeholder={t('selectRetentionTime')} />
                   </SelectTrigger>
                   <SelectContent>
@@ -554,15 +561,22 @@ export function SecurityTab({ configs, systemConfigsQuery }: SecurityTabProps) {
             onCheckedChange={(checked) =>
               handleToggle('cap_login_enabled', checked)
             }
+            aria-label={t('loginCaptchaEnabled')}
           />
         </CardHeader>
         <CardContent className='pt-6'>
           {/* 自动开始计算 Switch */}
           <div className='flex items-center justify-between rounded-xl border border-dashed p-4 bg-card mb-4'>
             <div className='space-y-0.5'>
-              <p className='text-sm font-semibold'>{t('autoStartSolving')}</p>
+              <Label htmlFor='cap_auto_solve' className='text-sm font-semibold'>
+                {t('autoStartSolving')}
+              </Label>
             </div>
-            <Switch checked={capAutoSolve} onCheckedChange={setCapAutoSolve} />
+            <Switch
+              id='cap_auto_solve'
+              checked={capAutoSolve}
+              onCheckedChange={setCapAutoSolve}
+            />
           </div>
           <form onSubmit={handleCapSave} className='space-y-6'>
             <div className='grid grid-cols-1 sm:grid-cols-2 gap-4'>