SEO 优化：补全 canonical、og:image、JSON-LD 及页面描述

Layout.astro:
- 新增 <link rel="canonical">，og:url / twitter:url 统一使用规范链接
- 新增 og:image / twitter:image：文章封面为绝对或 public URL 时使用封面，
  否则回退站点 favicon-192 并将 twitter:card 从 summary_large_image
  降级为 summary，避免声明大图卡片却无图
- banner 判断改用 typeof 收窄，兼容 404 页传入 banner={false} 的情况

posts/[...slug].astro (JSON-LD BlogPosting):
- 新增 dateModified（读取 frontmatter 的 updated 字段）
- 新增 image（仅绝对 URL 封面）和 mainEntityOfPage
- 移除遗留的 TODO 注释

页面 meta description：
- archive / friends / expenses / series 四个页面补充独立描述，
  不再退化为用页面标题填充

astro.config.mjs:
- sitemap 增加 filter 排除 /archive/，与 robots.txt 的
  Disallow: /archive/ 保持一致，消除收录信号矛盾

astro.config.mjs

@@ -102,7 +102,9 @@ export default defineConfig({
 			}
 		}),
         svelte(),
-		sitemap(),
+		sitemap({
+			filter: (page) => !page.includes("/archive/"),
+		}),
 	],
 	markdown: {
 		remarkPlugins: [

src/layouts/Layout.astro

@@ -30,6 +30,21 @@ interface Props {
 
 let { title, banner, description, lang, setOGTypeArticle } = Astro.props;
 
+// canonical URL
+const canonicalUrl = new URL(Astro.url.pathname, Astro.site).href;
+
+// social share image: use the page's own image if it's an absolute or public URL,
+// otherwise fall back to the site favicon with a smaller "summary" card
+let ogImage: string | undefined;
+if (typeof banner === "string" && /^https?:\/\//.test(banner)) {
+	ogImage = banner;
+} else if (typeof banner === "string" && banner.startsWith("/")) {
+	ogImage = new URL(url(banner), Astro.site).href;
+}
+const twitterCard = ogImage ? "summary_large_image" : "summary";
+const ogImageUrl =
+	ogImage ?? new URL(url("/favicon/favicon-light-192.png"), Astro.site).href;
+
 // apply a class to the body element to decide the height of the banner, only used for initial page load
 // Swup can update the body for each page visit, but it's after the page transition, causing a delay for banner height change
 // so use Swup hooks instead to change the height immediately when a link is clicked
@@ -83,21 +98,24 @@ const bannerOffset =
 		<meta charset="UTF-8" />
 		<meta name="description" content={description || pageTitle}>
 		<meta name="author" content={profileConfig.name}>
+		<link rel="canonical" href={canonicalUrl}>
 
 		<meta property="og:site_name" content={siteConfig.title}>
-		<meta property="og:url" content={Astro.url}>
+		<meta property="og:url" content={canonicalUrl}>
 		<meta property="og:title" content={pageTitle}>
 		<meta property="og:description" content={description || pageTitle}>
+		<meta property="og:image" content={ogImageUrl}>
 		{setOGTypeArticle ? (
         <meta property="og:type" content="article" />
         ) : (
         <meta property="og:type" content="website" />
         )}
 
-		<meta name="twitter:card" content="summary_large_image">
-		<meta property="twitter:url" content={Astro.url}>
+		<meta name="twitter:card" content={twitterCard}>
+		<meta property="twitter:url" content={canonicalUrl}>
 		<meta name="twitter:title" content={pageTitle}>
 		<meta name="twitter:description" content={description || pageTitle}>
+		<meta name="twitter:image" content={ogImageUrl}>
 
 		<meta name="viewport" content="width=device-width" />
 		<meta name="generator" content={Astro.generator} />

src/pages/archive.astro

@@ -3,12 +3,13 @@ import ArchivePanel from "@components/ArchivePanel.svelte";
 import I18nKey from "@i18n/i18nKey";
 import { i18n } from "@i18n/translation";
 import MainGridLayout from "@layouts/MainGridLayout.astro";
+import { siteConfig } from "@/config";
 import { getSortedPostsList } from "../utils/content-utils";
 
 const sortedPostsList = await getSortedPostsList();
 ---
 
-<MainGridLayout title={i18n(I18nKey.archive)}>
+<MainGridLayout title={i18n(I18nKey.archive)} description={`${siteConfig.title}的全部文章归档，按时间浏览所有博客文章。`}>
     <ArchivePanel sortedPosts={sortedPostsList} client:only="svelte"></ArchivePanel>
 </MainGridLayout>
 

src/pages/expenses.astro

@@ -56,7 +56,7 @@ const historyData = [
 ];
 ---
 
-<MainGridLayout title="运行成本">
+<MainGridLayout title="运行成本" description="本博客的运行成本明细，包括域名、CDN 等固定支出记录。">
     <div class="card-base p-6 md:p-8">
         
         <div class="flex items-center gap-2 mb-6">

src/pages/friends.astro

@@ -66,7 +66,7 @@ const friends = [
 ];
 ---
 
-<MainGridLayout title="友链">
+<MainGridLayout title="友链" description="友情链接页面，收录了一些朋友的博客与网站。">
     <!-- 头部 -->
     <div class="flex items-center gap-4 mb-8 mt-4 px-2">
         <div class="avatar">

src/pages/posts/[...slug].astro

@@ -28,6 +28,11 @@ const { Content, headings } = await entry.render();
 
 const { remarkPluginFrontmatter } = await entry.render();
 
+const postUrl = new URL(getPostUrlBySlug(entry.slug), Astro.site).href;
+const coverImage = /^https?:\/\//.test(entry.data.image)
+	? entry.data.image
+	: undefined;
+
 const jsonLd = {
 	"@context": "https://schema.org",
 	"@type": "BlogPosting",
@@ -40,10 +45,17 @@ const jsonLd = {
 		url: Astro.site,
 	},
 	datePublished: formatDateToYYYYMMDD(entry.data.published),
+	...(entry.data.updated && {
+		dateModified: formatDateToYYYYMMDD(entry.data.updated),
+	}),
+	...(coverImage && { image: coverImage }),
+	mainEntityOfPage: {
+		"@type": "WebPage",
+		"@id": postUrl,
+	},
 	inLanguage: entry.data.lang
 		? entry.data.lang.replace("_", "-")
 		: siteConfig.lang.replace("_", "-"),
-	// TODO include cover image here
 };
 ---
 <MainGridLayout banner={entry.data.image} title={entry.data.title} description={entry.data.description} lang={entry.data.lang} setOGTypeArticle={true} headings={headings} series={entry.data.series}>

src/pages/series.astro

@@ -5,6 +5,6 @@ import { i18n } from '@i18n/translation'
 import I18nKey from '@i18n/i18nKey'
 ---
 
-<MainGridLayout title={i18n(I18nKey.series)}>
+<MainGridLayout title={i18n(I18nKey.series)} description="按系列浏览博客文章，查看同一主题下的连载内容。">
     <SeriesPanel></SeriesPanel>
 </MainGridLayout>