feat(channel-monitor): add feature switch settings + fix extra_models save

Settings:
- New "功能开关" tab between 通用设置 and 安全与认证
- ChannelMonitorEnabled toggle: runner skips scheduling when false,
  user-facing list returns empty
- ChannelMonitorDefaultIntervalSeconds (15-3600): pre-fills interval
  when creating a new monitor; each monitor can still override

Bug fix:
- ModelTagInput now commits pending input on blur, not just Enter/Tab.
  Previously clicking "save" with an un-Enter'd extra model would drop
  the value (DB stored extra_models=[] even when user typed entries).

Backend:
- domain_constants: SettingKeyChannelMonitor{Enabled,DefaultIntervalSeconds}
- SettingService.GetChannelMonitorRuntime: lightweight getter used by
  runner tick + user handler per-request (fail-open on DB error)
- Runner tickDueChecks: bails early when feature disabled
- ChannelMonitorUserHandler: checks feature flag before serving
- Comment on runner doc: scheduler state is implicit (every tick re-reads
  ListEnabled from DB), so CRUD ops on monitors self-maintain the schedule

Bump VERSION to 0.1.114.25

frontend/src/views/admin/SettingsView.vue

@@ -3749,6 +3749,52 @@
         </div>
         <!-- /Tab: General -->
 
+        <!-- Tab: Features (功能开关) -->
+        <div v-show="activeTab === 'features'" class="space-y-6">
+
+        <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.features.channelMonitor.title') }}
+            </h2>
+            <p class="mt-1 text-sm text-gray-500 dark:text-gray-400">
+              {{ t('admin.settings.features.channelMonitor.description') }}
+            </p>
+          </div>
+          <div class="space-y-5 p-6">
+            <div class="flex items-center justify-between">
+              <div>
+                <label class="text-sm font-medium text-gray-700 dark:text-gray-300">
+                  {{ t('admin.settings.features.channelMonitor.enabled') }}
+                </label>
+                <p class="mt-0.5 text-xs text-gray-500 dark:text-gray-400">
+                  {{ t('admin.settings.features.channelMonitor.enabledHint') }}
+                </p>
+              </div>
+              <Toggle v-model="form.channel_monitor_enabled" />
+            </div>
+
+            <div v-if="form.channel_monitor_enabled">
+              <label class="input-label">
+                {{ t('admin.settings.features.channelMonitor.defaultInterval') }}
+                <span class="text-red-500">*</span>
+              </label>
+              <input
+                v-model.number="form.channel_monitor_default_interval_seconds"
+                type="number"
+                min="15"
+                max="3600"
+                class="input"
+              />
+              <p class="mt-1 text-xs text-gray-400">
+                {{ t('admin.settings.features.channelMonitor.defaultIntervalHint') }}
+              </p>
+            </div>
+          </div>
+        </div>
+
+        </div><!-- /Tab: Features -->
+
         <!-- Tab: Email -->
         <!-- Tab: Payment -->
         <div v-show="activeTab === 'payment'" class="space-y-6">
@@ -4737,6 +4783,7 @@ const paymentMethodsHref = computed(() =>
 
 type SettingsTab =
   | "general"
+  | "features"
   | "security"
   | "users"
   | "gateway"
@@ -4746,6 +4793,7 @@ type SettingsTab =
 const activeTab = ref<SettingsTab>("general");
 const settingsTabs = [
   { key: "general" as SettingsTab, icon: "home" as const },
+  { key: "features" as SettingsTab, icon: "bolt" as const },
   { key: "security" as SettingsTab, icon: "shield" as const },
   { key: "users" as SettingsTab, icon: "user" as const },
   { key: "gateway" as SettingsTab, icon: "server" as const },
@@ -5005,6 +5053,9 @@ const form = reactive<SettingsForm>({
   balance_low_notify_recharge_url: "",
   account_quota_notify_enabled: false,
   account_quota_notify_emails: [] as NotifyEmailEntry[],
+  // Channel Monitor feature switch
+  channel_monitor_enabled: true,
+  channel_monitor_default_interval_seconds: 60,
 });
 
 const authSourceDefaults = reactive<AuthSourceDefaultsState>(
@@ -5912,6 +5963,10 @@ async function saveSettings() {
       account_quota_notify_emails: (
         form.account_quota_notify_emails || []
       ).filter((e) => e.email.trim() !== ""),
+      // Channel Monitor feature switch
+      channel_monitor_enabled: form.channel_monitor_enabled,
+      channel_monitor_default_interval_seconds:
+        Number(form.channel_monitor_default_interval_seconds) || 60,
     };
 
     appendAuthSourceDefaultsToUpdateRequest(payload, authSourceDefaults);