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.

backend/src/controllers/admin_api.rs

@@ -208,6 +208,7 @@ pub struct AdminSiteSettingsResponse {
     pub media_r2_secret_access_key: Option<String>,
     pub seo_default_og_image: Option<String>,
     pub seo_default_twitter_handle: Option<String>,
+    pub seo_wechat_share_qr_enabled: bool,
     pub notification_webhook_url: Option<String>,
     pub notification_channel_type: String,
     pub notification_comment_enabled: bool,
@@ -827,6 +828,7 @@ fn build_settings_response(
         media_r2_secret_access_key: item.media_r2_secret_access_key,
         seo_default_og_image: item.seo_default_og_image,
         seo_default_twitter_handle: item.seo_default_twitter_handle,
+        seo_wechat_share_qr_enabled: item.seo_wechat_share_qr_enabled.unwrap_or(false),
         notification_webhook_url: item.notification_webhook_url,
         notification_channel_type: item
             .notification_channel_type