feat: add 529 overload cooldown toggle and duration settings in admin gateway page

Move 529 overload cooldown configuration from config file to admin
settings UI. Adds an enable/disable toggle and configurable cooldown
duration (1-120 min) under /admin/settings gateway tab, stored as
JSON in the settings table.

When disabled, 529 errors are logged but accounts are no longer
paused from scheduling. Falls back to config file value when DB
is unreachable or settingService is nil.

frontend/src/views/admin/SettingsView.vue

@@ -168,8 +168,93 @@
         </div>
         </div><!-- /Tab: Security — Admin API Key -->
 
-        <!-- Tab: Gateway — Stream Timeout -->
+        <!-- Tab: Gateway -->
         <div v-show="activeTab === 'gateway'" class="space-y-6">
+
+        <!-- Overload Cooldown (529) Settings -->
+        <div class="card">
+          <div class="border-b border-gray-100 px-6 py-4 dark:border-dark-700">
+            <h2 class="text-lg font-semibold text-gray-900 dark:text-white">
+              {{ t('admin.settings.overloadCooldown.title') }}
+            </h2>
+            <p class="mt-1 text-sm text-gray-500 dark:text-gray-400">
+              {{ t('admin.settings.overloadCooldown.description') }}
+            </p>
+          </div>
+          <div class="space-y-5 p-6">
+            <div v-if="overloadCooldownLoading" class="flex items-center gap-2 text-gray-500">
+              <div class="h-4 w-4 animate-spin rounded-full border-b-2 border-primary-600"></div>
+              {{ t('common.loading') }}
+            </div>
+
+            <template v-else>
+              <div class="flex items-center justify-between">
+                <div>
+                  <label class="font-medium text-gray-900 dark:text-white">{{
+                    t('admin.settings.overloadCooldown.enabled')
+                  }}</label>
+                  <p class="text-sm text-gray-500 dark:text-gray-400">
+                    {{ t('admin.settings.overloadCooldown.enabledHint') }}
+                  </p>
+                </div>
+                <Toggle v-model="overloadCooldownForm.enabled" />
+              </div>
+
+              <div
+                v-if="overloadCooldownForm.enabled"
+                class="space-y-4 border-t border-gray-100 pt-4 dark:border-dark-700"
+              >
+                <div>
+                  <label class="mb-2 block text-sm font-medium text-gray-700 dark:text-gray-300">
+                    {{ t('admin.settings.overloadCooldown.cooldownMinutes') }}
+                  </label>
+                  <input
+                    v-model.number="overloadCooldownForm.cooldown_minutes"
+                    type="number"
+                    min="1"
+                    max="120"
+                    class="input w-32"
+                  />
+                  <p class="mt-1.5 text-xs text-gray-500 dark:text-gray-400">
+                    {{ t('admin.settings.overloadCooldown.cooldownMinutesHint') }}
+                  </p>
+                </div>
+              </div>
+
+              <div class="flex justify-end border-t border-gray-100 pt-4 dark:border-dark-700">
+                <button
+                  type="button"
+                  @click="saveOverloadCooldownSettings"
+                  :disabled="overloadCooldownSaving"
+                  class="btn btn-primary btn-sm"
+                >
+                  <svg
+                    v-if="overloadCooldownSaving"
+                    class="mr-1 h-4 w-4 animate-spin"
+                    fill="none"
+                    viewBox="0 0 24 24"
+                  >
+                    <circle
+                      class="opacity-25"
+                      cx="12"
+                      cy="12"
+                      r="10"
+                      stroke="currentColor"
+                      stroke-width="4"
+                    ></circle>
+                    <path
+                      class="opacity-75"
+                      fill="currentColor"
+                      d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"
+                    ></path>
+                  </svg>
+                  {{ overloadCooldownSaving ? t('common.saving') : t('common.save') }}
+                </button>
+              </div>
+            </template>
+          </div>
+        </div>
+
         <!-- Stream Timeout Settings -->
         <div class="card">
           <div class="border-b border-gray-100 px-6 py-4 dark:border-dark-700">
@@ -1765,6 +1850,14 @@ const adminApiKeyOperating = ref(false)
 const newAdminApiKey = ref('')
 const subscriptionGroups = ref<AdminGroup[]>([])
 
+// Overload Cooldown (529) 状态
+const overloadCooldownLoading = ref(true)
+const overloadCooldownSaving = ref(false)
+const overloadCooldownForm = reactive({
+  enabled: true,
+  cooldown_minutes: 10
+})
+
 // Stream Timeout 状态
 const streamTimeoutLoading = ref(true)
 const streamTimeoutSaving = ref(false)
@@ -2274,6 +2367,37 @@ function copyNewKey() {
     })
 }
 
+// Overload Cooldown 方法
+async function loadOverloadCooldownSettings() {
+  overloadCooldownLoading.value = true
+  try {
+    const settings = await adminAPI.settings.getOverloadCooldownSettings()
+    Object.assign(overloadCooldownForm, settings)
+  } catch (error: any) {
+    console.error('Failed to load overload cooldown settings:', error)
+  } finally {
+    overloadCooldownLoading.value = false
+  }
+}
+
+async function saveOverloadCooldownSettings() {
+  overloadCooldownSaving.value = true
+  try {
+    const updated = await adminAPI.settings.updateOverloadCooldownSettings({
+      enabled: overloadCooldownForm.enabled,
+      cooldown_minutes: overloadCooldownForm.cooldown_minutes
+    })
+    Object.assign(overloadCooldownForm, updated)
+    appStore.showSuccess(t('admin.settings.overloadCooldown.saved'))
+  } catch (error: any) {
+    appStore.showError(
+      t('admin.settings.overloadCooldown.saveFailed') + ': ' + (error.message || t('common.unknownError'))
+    )
+  } finally {
+    overloadCooldownSaving.value = false
+  }
+}
+
 // Stream Timeout 方法
 async function loadStreamTimeoutSettings() {
   streamTimeoutLoading.value = true
@@ -2396,6 +2520,7 @@ onMounted(() => {
   loadSettings()
   loadSubscriptionGroups()
   loadAdminApiKey()
+  loadOverloadCooldownSettings()
   loadStreamTimeoutSettings()
   loadRectifierSettings()
   loadBetaPolicySettings()