Merge upstream/main: v0.1.62-v0.1.64 updates

Major updates:
- fix(gateway): fix SSE streaming usage data overwrite issue
- feat(purchase): add purchase subscription iframe page and config
- fix(scheduler): fix race condition from empty cache
- feat(settings): add PurchaseSubscriptionEnabled and PurchaseSubscriptionURL

Resolved conflicts:
- backend/cmd/server/VERSION: updated to 0.1.61
- setting_service.go: keep TianShuAPI site name while adding purchase subscription features

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/views/admin/SettingsView.vue

@@ -935,6 +935,51 @@
           </div>
         </div>
 
+        <!-- Purchase Subscription Page -->
+        <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.purchase.title') }}
+            </h2>
+            <p class="mt-1 text-sm text-gray-500 dark:text-gray-400">
+              {{ t('admin.settings.purchase.description') }}
+            </p>
+          </div>
+          <div class="space-y-6 p-6">
+            <!-- Enable Toggle -->
+            <div class="flex items-center justify-between">
+              <div>
+                <label class="font-medium text-gray-900 dark:text-white">{{
+                  t('admin.settings.purchase.enabled')
+                }}</label>
+                <p class="text-sm text-gray-500 dark:text-gray-400">
+                  {{ t('admin.settings.purchase.enabledHint') }}
+                </p>
+              </div>
+              <Toggle v-model="form.purchase_subscription_enabled" />
+            </div>
+
+            <!-- URL -->
+            <div>
+              <label class="mb-2 block text-sm font-medium text-gray-700 dark:text-gray-300">
+                {{ t('admin.settings.purchase.url') }}
+              </label>
+              <input
+                v-model="form.purchase_subscription_url"
+                type="url"
+                class="input font-mono text-sm"
+                :placeholder="t('admin.settings.purchase.urlPlaceholder')"
+              />
+              <p class="mt-1.5 text-xs text-gray-500 dark:text-gray-400">
+                {{ t('admin.settings.purchase.urlHint') }}
+              </p>
+              <p class="mt-2 text-xs text-amber-600 dark:text-amber-400">
+                {{ t('admin.settings.purchase.iframeWarning') }}
+              </p>
+            </div>
+          </div>
+        </div>
+
         <!-- Send Test Email - Only show when email verification is enabled -->
         <div v-if="form.email_verify_enabled" class="card">
           <div class="border-b border-gray-100 px-6 py-4 dark:border-dark-700">
@@ -1083,6 +1128,8 @@ const form = reactive<SettingsForm>({
   doc_url: '',
   home_content: '',
   hide_ccs_import_button: false,
+  purchase_subscription_enabled: false,
+  purchase_subscription_url: '',
   smtp_host: '',
   smtp_port: 587,
   smtp_username: '',
@@ -1208,6 +1255,8 @@ async function saveSettings() {
       doc_url: form.doc_url,
       home_content: form.home_content,
       hide_ccs_import_button: form.hide_ccs_import_button,
+      purchase_subscription_enabled: form.purchase_subscription_enabled,
+      purchase_subscription_url: form.purchase_subscription_url,
       smtp_host: form.smtp_host,
       smtp_port: form.smtp_port,
       smtp_username: form.smtp_username,