feat(notify): add platform/ID to quota alert email, add recharge URL to balance alert

- Quota alert email now shows account ID and platform
- Balance low email includes a "Top Up Now" button when recharge URL is configured
- New setting: balance_low_notify_recharge_url in admin settings

frontend/src/api/admin/settings.ts

@@ -138,6 +138,7 @@ export interface SystemSettings {
   // Balance & quota notification
   balance_low_notify_enabled: boolean
   balance_low_notify_threshold: number
+  balance_low_notify_recharge_url: string
   account_quota_notify_enabled: boolean
   account_quota_notify_emails: NotifyEmailEntry[]
 }
@@ -242,6 +243,7 @@ export interface UpdateSettingsRequest {
   // Balance & quota notification
   balance_low_notify_enabled?: boolean
   balance_low_notify_threshold?: number
+  balance_low_notify_recharge_url?: string
   account_quota_notify_enabled?: boolean
   account_quota_notify_emails?: NotifyEmailEntry[]
 }

frontend/src/i18n/locales/en.ts

@@ -4649,6 +4649,9 @@ export default {
         threshold: 'Default Threshold',
         thresholdHint: 'Used when user has not set a custom value',
         thresholdPlaceholder: 'Enter amount',
+        rechargeUrl: 'Recharge Page URL',
+        rechargeUrlPlaceholder: 'https://example.com/payment',
+        rechargeUrlHint: 'A top-up button will appear in the email when set',
       },
       quotaNotify: {
         title: 'Account Quota Notification',

frontend/src/i18n/locales/zh.ts

@@ -4813,6 +4813,9 @@ export default {
         threshold: '默认提醒阈值',
         thresholdHint: '用户未自定义时使用此值',
         thresholdPlaceholder: '输入金额',
+        rechargeUrl: '充值页面 URL',
+        rechargeUrlPlaceholder: 'https://example.com/payment',
+        rechargeUrlHint: '设置后邮件中将包含充值链接按钮',
       },
       quotaNotify: {
         title: '账号限额通知',

frontend/src/views/admin/SettingsView.vue

@@ -2705,6 +2705,11 @@
               </div>
               <p class="mt-1 text-xs text-gray-500 dark:text-gray-400">{{ t('admin.settings.balanceNotify.thresholdHint') }}</p>
             </div>
+            <div>
+              <label class="mb-2 block text-sm font-medium text-gray-700 dark:text-gray-300">{{ t('admin.settings.balanceNotify.rechargeUrl') }}</label>
+              <input v-model="form.balance_low_notify_recharge_url" type="url" class="input" :placeholder="t('admin.settings.balanceNotify.rechargeUrlPlaceholder')" />
+              <p class="mt-1 text-xs text-gray-500 dark:text-gray-400">{{ t('admin.settings.balanceNotify.rechargeUrlHint') }}</p>
+            </div>
           </div>
         </div>
 
@@ -3027,6 +3032,7 @@ const form = reactive<SettingsForm>({
   // Balance & quota notification
   balance_low_notify_enabled: false,
   balance_low_notify_threshold: 0,
+  balance_low_notify_recharge_url: '',
   account_quota_notify_enabled: false,
   account_quota_notify_emails: [] as NotifyEmailEntry[]
 })
@@ -3598,6 +3604,7 @@ async function saveSettings() {
       // Balance & quota notification
       balance_low_notify_enabled: form.balance_low_notify_enabled,
       balance_low_notify_threshold: Number(form.balance_low_notify_threshold) || 0,
+      balance_low_notify_recharge_url: form.balance_low_notify_recharge_url || '',
       account_quota_notify_enabled: form.account_quota_notify_enabled,
       account_quota_notify_emails: (form.account_quota_notify_emails || []).filter((e) => e.email.trim() !== ''),
     }