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/index.astro

@@ -1,5 +1,8 @@
 ---
 import BaseLayout from '../layouts/BaseLayout.astro';
+import DiscoveryBrief from '../components/seo/DiscoveryBrief.astro';
+import PageViewTracker from '../components/seo/PageViewTracker.astro';
+import SharePanel from '../components/seo/SharePanel.astro';
 import TerminalWindow from '../components/ui/TerminalWindow.astro';
 import CommandPrompt from '../components/ui/CommandPrompt.astro';
 import FilterPill from '../components/ui/FilterPill.astro';
@@ -12,6 +15,7 @@ import TechStackList from '../components/TechStackList.astro';
 import { terminalConfig } from '../lib/config/terminal';
 import { api, DEFAULT_SITE_SETTINGS } from '../lib/api/client';
 import { formatReadTime, getI18n } from '../lib/i18n';
+import { buildDiscoveryHighlights, buildFaqJsonLd, buildPageFaqs, buildPostItemList } from '../lib/seo';
 import type { AppFriendLink } from '../lib/api/client';
 import type { ContentOverview, ContentWindowHighlight, PopularPostHighlight, Post } from '../lib/types';
 import { getAccentVars, getCategoryTheme, getPostTypeTheme, getTagTheme } from '../lib/utils';
@@ -63,6 +67,7 @@ let contentOverview: ContentOverview = {
 };
 let apiError: string | null = null;
 const { locale, t } = getI18n(Astro);
+const isEnglish = locale.startsWith('en');
 
 const formatDurationMs = (value: number | undefined) => {
   if (!value || value <= 0) return locale === 'en' ? 'N/A' : '暂无';
@@ -221,9 +226,68 @@ const navLinks = [
   { icon: 'fa-user-secret', text: t('nav.about'), href: '/about' },
   ...(siteSettings.ai.enabled ? [{ icon: 'fa-robot', text: t('nav.ask'), href: '/ask' }] : []),
 ];
+const siteBaseUrl = (siteSettings.siteUrl || new URL(Astro.request.url).origin).replace(/\/$/, '');
+const homeJsonLd = [
+  {
+    '@context': 'https://schema.org',
+    '@type': 'CollectionPage',
+    name: siteSettings.siteTitle,
+    description: siteSettings.siteDescription,
+    url: siteBaseUrl,
+    inLanguage: locale,
+  },
+  {
+    '@context': 'https://schema.org',
+    '@type': 'ItemList',
+    name: `${siteSettings.siteName} recent posts`,
+    itemListElement: buildPostItemList(recentPosts, siteBaseUrl),
+  },
+];
+const homeShareCopy = isEnglish
+  ? {
+      badge: 'site entry',
+      title: 'Share the homepage',
+      description:
+        'Use the homepage as the canonical top-level entry for people and AI search to branch into articles, taxonomies, reviews, and profile context.',
+    }
+    : {
+      badge: '站点入口',
+      title: '分享首页总入口',
+      description: '把首页当成站点的规范总入口分发出去，方便用户和 AI 搜索继续进入文章、分类、评测和个人介绍等核心页面。',
+    };
+const homeBriefHighlights = buildDiscoveryHighlights([
+  siteSettings.siteDescription,
+  siteSettings.heroSubtitle,
+  siteSettings.ownerBio,
+  `${t('common.posts')}: ${allPosts.length}`,
+  `${t('common.categories')}: ${categories.length}`,
+  `${t('common.tags')}: ${tags.length}`,
+]);
+const homeFaqs = buildPageFaqs({
+  locale,
+  pageTitle: siteSettings.siteTitle,
+  summary: siteSettings.heroSubtitle || siteSettings.siteDescription,
+  primaryLabel: isEnglish ? 'homepage' : '首页',
+  primaryUrl: siteBaseUrl,
+  relatedLinks: [
+    { label: t('nav.articles'), url: `${siteBaseUrl}/articles` },
+    { label: t('nav.categories'), url: `${siteBaseUrl}/categories` },
+    { label: t('nav.about'), url: `${siteBaseUrl}/about` },
+  ],
+  signals: homeBriefHighlights,
+});
+const homeFaqJsonLd = buildFaqJsonLd(homeFaqs);
 ---
 
-<BaseLayout title={siteSettings.siteTitle} description={siteSettings.siteDescription} siteSettings={siteSettings}>
+<BaseLayout
+  title={siteSettings.siteTitle}
+  description={siteSettings.siteDescription}
+  siteSettings={siteSettings}
+  canonical="/"
+  noindex={hasActiveFilters}
+  jsonLd={[...homeJsonLd, homeFaqJsonLd].filter(Boolean)}
+>
+  <PageViewTracker pageType="home" entityId="homepage" />
   <div class="max-w-5xl mx-auto px-4 sm:px-6 lg:px-8 py-6">
     <TerminalWindow title={terminalConfig.title} class="w-full">
       <div class="mb-5 px-4 overflow-x-auto">
@@ -266,6 +330,31 @@ const navLinks = [
             </a>
           ))}
         </div>
+
+        <div class="ml-4 mt-4">
+          <SharePanel
+            shareTitle={siteSettings.siteTitle}
+            summary={siteSettings.heroSubtitle || siteSettings.siteDescription}
+            canonicalUrl={siteBaseUrl}
+            badge={homeShareCopy.badge}
+            kicker="geo / homepage"
+            title={homeShareCopy.title}
+            description={homeShareCopy.description}
+            stats={systemStats.slice(0, 4)}
+            wechatShareQrEnabled={siteSettings.seo.wechatShareQrEnabled}
+          />
+        </div>
+
+        <div class="ml-4 mt-4">
+          <DiscoveryBrief
+            badge={isEnglish ? 'site brief' : '站点摘要'}
+            kicker="geo / overview"
+            title={isEnglish ? 'AI-readable site brief' : '给 AI 看的站点摘要'}
+            summary={siteSettings.heroSubtitle || siteSettings.siteDescription}
+            highlights={homeBriefHighlights}
+            faqs={homeFaqs}
+          />
+        </div>
       </div>
 
       {apiError && (