feat(notify): add balance low & account quota notification system

- User balance low notification: email alert when balance drops below
  configurable threshold (user email + verified extra emails)
- Account quota notification: broadcast email to admin-configured
  recipients when daily/weekly/total quota usage exceeds alert threshold
- Admin settings: global enable/disable, default threshold, quota
  notification email list (Email Settings tab)
- User profile: enable/disable, custom threshold, add/remove extra
  notification emails with verification code flow
- Account quota: per-dimension alert toggle and threshold in quota
  control card
- Trigger logic: first-crossing only (old >= threshold && new < threshold
  for balance; old < threshold && new >= threshold for quota), naturally
  prevents duplicate notifications without Redis dedup

frontend/src/components/account/EditAccountModal.vue

@@ -1186,6 +1186,12 @@
           :weeklyResetDay="editWeeklyResetDay"
           :weeklyResetHour="editWeeklyResetHour"
           :resetTimezone="editResetTimezone"
+          :quotaNotifyDailyEnabled="editQuotaNotifyDailyEnabled"
+          :quotaNotifyDailyThreshold="editQuotaNotifyDailyThreshold"
+          :quotaNotifyWeeklyEnabled="editQuotaNotifyWeeklyEnabled"
+          :quotaNotifyWeeklyThreshold="editQuotaNotifyWeeklyThreshold"
+          :quotaNotifyTotalEnabled="editQuotaNotifyTotalEnabled"
+          :quotaNotifyTotalThreshold="editQuotaNotifyTotalThreshold"
           @update:totalLimit="editQuotaLimit = $event"
           @update:dailyLimit="editQuotaDailyLimit = $event"
           @update:weeklyLimit="editQuotaWeeklyLimit = $event"
@@ -1195,6 +1201,12 @@
           @update:weeklyResetDay="editWeeklyResetDay = $event"
           @update:weeklyResetHour="editWeeklyResetHour = $event"
           @update:resetTimezone="editResetTimezone = $event"
+          @update:quotaNotifyDailyEnabled="editQuotaNotifyDailyEnabled = $event"
+          @update:quotaNotifyDailyThreshold="editQuotaNotifyDailyThreshold = $event"
+          @update:quotaNotifyWeeklyEnabled="editQuotaNotifyWeeklyEnabled = $event"
+          @update:quotaNotifyWeeklyThreshold="editQuotaNotifyWeeklyThreshold = $event"
+          @update:quotaNotifyTotalEnabled="editQuotaNotifyTotalEnabled = $event"
+          @update:quotaNotifyTotalThreshold="editQuotaNotifyTotalThreshold = $event"
         />
       </div>
       <!-- 配额控制 (非 Anthropic apikey/bedrock) -->
@@ -1218,6 +1230,12 @@
           :weeklyResetDay="editWeeklyResetDay"
           :weeklyResetHour="editWeeklyResetHour"
           :resetTimezone="editResetTimezone"
+          :quotaNotifyDailyEnabled="editQuotaNotifyDailyEnabled"
+          :quotaNotifyDailyThreshold="editQuotaNotifyDailyThreshold"
+          :quotaNotifyWeeklyEnabled="editQuotaNotifyWeeklyEnabled"
+          :quotaNotifyWeeklyThreshold="editQuotaNotifyWeeklyThreshold"
+          :quotaNotifyTotalEnabled="editQuotaNotifyTotalEnabled"
+          :quotaNotifyTotalThreshold="editQuotaNotifyTotalThreshold"
           @update:totalLimit="editQuotaLimit = $event"
           @update:dailyLimit="editQuotaDailyLimit = $event"
           @update:weeklyLimit="editQuotaWeeklyLimit = $event"
@@ -1227,6 +1245,12 @@
           @update:weeklyResetDay="editWeeklyResetDay = $event"
           @update:weeklyResetHour="editWeeklyResetHour = $event"
           @update:resetTimezone="editResetTimezone = $event"
+          @update:quotaNotifyDailyEnabled="editQuotaNotifyDailyEnabled = $event"
+          @update:quotaNotifyDailyThreshold="editQuotaNotifyDailyThreshold = $event"
+          @update:quotaNotifyWeeklyEnabled="editQuotaNotifyWeeklyEnabled = $event"
+          @update:quotaNotifyWeeklyThreshold="editQuotaNotifyWeeklyThreshold = $event"
+          @update:quotaNotifyTotalEnabled="editQuotaNotifyTotalEnabled = $event"
+          @update:quotaNotifyTotalThreshold="editQuotaNotifyTotalThreshold = $event"
         />
       </div>
 
@@ -1960,6 +1984,12 @@ const editWeeklyResetMode = ref<'rolling' | 'fixed' | null>(null)
 const editWeeklyResetDay = ref<number | null>(null)
 const editWeeklyResetHour = ref<number | null>(null)
 const editResetTimezone = ref<string | null>(null)
+const editQuotaNotifyDailyEnabled = ref<boolean | null>(null)
+const editQuotaNotifyDailyThreshold = ref<number | null>(null)
+const editQuotaNotifyWeeklyEnabled = ref<boolean | null>(null)
+const editQuotaNotifyWeeklyThreshold = ref<number | null>(null)
+const editQuotaNotifyTotalEnabled = ref<boolean | null>(null)
+const editQuotaNotifyTotalThreshold = ref<number | null>(null)
 const openAIWSModeOptions = computed(() => [
   { value: OPENAI_WS_MODE_OFF, label: t('admin.accounts.openai.wsModeOff') },
   // TODO: ctx_pool 选项暂时隐藏，待测试完成后恢复
@@ -2159,6 +2189,13 @@ const syncFormFromAccount = (newAccount: Account | null) => {
     editWeeklyResetDay.value = (extra?.quota_weekly_reset_day as number) ?? null
     editWeeklyResetHour.value = (extra?.quota_weekly_reset_hour as number) ?? null
     editResetTimezone.value = (extra?.quota_reset_timezone as string) || null
+    // Load quota notify config
+    editQuotaNotifyDailyEnabled.value = (extra?.quota_notify_daily_enabled as boolean) ?? null
+    editQuotaNotifyDailyThreshold.value = (extra?.quota_notify_daily_threshold as number) ?? null
+    editQuotaNotifyWeeklyEnabled.value = (extra?.quota_notify_weekly_enabled as boolean) ?? null
+    editQuotaNotifyWeeklyThreshold.value = (extra?.quota_notify_weekly_threshold as number) ?? null
+    editQuotaNotifyTotalEnabled.value = (extra?.quota_notify_total_enabled as boolean) ?? null
+    editQuotaNotifyTotalThreshold.value = (extra?.quota_notify_total_threshold as number) ?? null
   } else {
     editQuotaLimit.value = null
     editQuotaDailyLimit.value = null
@@ -2169,6 +2206,12 @@ const syncFormFromAccount = (newAccount: Account | null) => {
     editWeeklyResetDay.value = null
     editWeeklyResetHour.value = null
     editResetTimezone.value = null
+    editQuotaNotifyDailyEnabled.value = null
+    editQuotaNotifyDailyThreshold.value = null
+    editQuotaNotifyWeeklyEnabled.value = null
+    editQuotaNotifyWeeklyThreshold.value = null
+    editQuotaNotifyTotalEnabled.value = null
+    editQuotaNotifyTotalThreshold.value = null
   }
 
   // Load antigravity model mapping (Antigravity 只支持映射模式)
@@ -2283,6 +2326,13 @@ const syncFormFromAccount = (newAccount: Account | null) => {
     editQuotaLimit.value = typeof bedrockExtra.quota_limit === 'number' ? bedrockExtra.quota_limit : null
     editQuotaDailyLimit.value = typeof bedrockExtra.quota_daily_limit === 'number' ? bedrockExtra.quota_daily_limit : null
     editQuotaWeeklyLimit.value = typeof bedrockExtra.quota_weekly_limit === 'number' ? bedrockExtra.quota_weekly_limit : null
+    // Load quota notify for bedrock
+    editQuotaNotifyDailyEnabled.value = (bedrockExtra.quota_notify_daily_enabled as boolean) ?? null
+    editQuotaNotifyDailyThreshold.value = (bedrockExtra.quota_notify_daily_threshold as number) ?? null
+    editQuotaNotifyWeeklyEnabled.value = (bedrockExtra.quota_notify_weekly_enabled as boolean) ?? null
+    editQuotaNotifyWeeklyThreshold.value = (bedrockExtra.quota_notify_weekly_threshold as number) ?? null
+    editQuotaNotifyTotalEnabled.value = (bedrockExtra.quota_notify_total_enabled as boolean) ?? null
+    editQuotaNotifyTotalThreshold.value = (bedrockExtra.quota_notify_total_threshold as number) ?? null
 
     // Load model mappings for bedrock
     const existingMappings = bedrockCreds.model_mapping as Record<string, string> | undefined
@@ -3198,6 +3248,40 @@ const handleSubmit = async () => {
       } else {
         delete newExtra.quota_reset_timezone
       }
+      // Quota notify config
+      if (editQuotaNotifyDailyEnabled.value) {
+        newExtra.quota_notify_daily_enabled = true
+        if (editQuotaNotifyDailyThreshold.value != null) {
+          newExtra.quota_notify_daily_threshold = editQuotaNotifyDailyThreshold.value
+        } else {
+          delete newExtra.quota_notify_daily_threshold
+        }
+      } else {
+        delete newExtra.quota_notify_daily_enabled
+        delete newExtra.quota_notify_daily_threshold
+      }
+      if (editQuotaNotifyWeeklyEnabled.value) {
+        newExtra.quota_notify_weekly_enabled = true
+        if (editQuotaNotifyWeeklyThreshold.value != null) {
+          newExtra.quota_notify_weekly_threshold = editQuotaNotifyWeeklyThreshold.value
+        } else {
+          delete newExtra.quota_notify_weekly_threshold
+        }
+      } else {
+        delete newExtra.quota_notify_weekly_enabled
+        delete newExtra.quota_notify_weekly_threshold
+      }
+      if (editQuotaNotifyTotalEnabled.value) {
+        newExtra.quota_notify_total_enabled = true
+        if (editQuotaNotifyTotalThreshold.value != null) {
+          newExtra.quota_notify_total_threshold = editQuotaNotifyTotalThreshold.value
+        } else {
+          delete newExtra.quota_notify_total_threshold
+        }
+      } else {
+        delete newExtra.quota_notify_total_enabled
+        delete newExtra.quota_notify_total_threshold
+      }
       updatePayload.extra = newExtra
     }