feat: add SharePanel component for social sharing with QR code support

- Implemented SharePanel component in `SharePanel.astro` for sharing content on social media platforms.
- Integrated QR code generation for WeChat sharing using the `qrcode` library.
- Added localization support for English and Chinese languages.
- Created utility functions in `seo.ts` for building article summaries and FAQs.
- Introduced API routes for serving IndexNow key and generating full LLM catalog and summaries.
- Enhanced SEO capabilities with structured data for articles and pages.

frontend/src/pages/subscriptions/manage.astro

@@ -55,7 +55,7 @@ const initialDisplayName = subscription?.display_name ?? '';
 const initialStatus = subscription?.status === 'paused' ? 'paused' : 'active';
 ---
 
-<BaseLayout title="管理订阅偏好" description="调整订阅偏好、暂停订阅或查看当前订阅状态。">
+<BaseLayout title="管理订阅偏好" description="调整订阅偏好、暂停订阅或查看当前订阅状态。" noindex>
   <section class="subscription-shell">
     <div class="subscription-card" data-subscription-manage-root data-api-base={apiBaseUrl}>
       <p class="subscription-kicker">subscriptions / manage</p>