refactor: 主题系统 → monorepo 五个独立网站

- packages/core: @aidir/core 底座库（src/pages 页面组件体 1:1 镜像路由树 / kit 站点外壳工厂 / content/blog / scripts）
- sites/: 5 个独立 Next.js 网站（ai-stack / launchai / the-ai-ledger / devai-tools / findai）
  - 每站独立 package.json / next.config / tailwind / messages / .env / 构建
  - src/app 约 56 个薄路由文件（re-export 底座页面 + 内联路由段配置 revalidate/dynamic）
  - src/site/brand.tsx 站点配置 + src/site/home.tsx 站点首页（createMarketingLayout / createHomePage 工厂）
- generate-site.mjs: 站点生成器（新增网站 = SITES 加条目，零 Core 修改）
- start-all-sites.sh: 一键启动 3001-3005
- next-config.mjs: 底座统一 Next 配置工厂（next-intl + MDX + standalone）
- 五站共享同一套 PostgreSQL / Better Auth / Admin（设计文档 §42）
- 验证: 5 站 build OK / typecheck OK / 55 路由冒烟 200 / 品牌-内容-截图 差异确认 / 登录-投票-重复检测 e2e PASS

sites/ai-stack/src/i18n/request.ts

@@ -0,0 +1,37 @@
+import { getRequestConfig } from "next-intl/server";
+import { notFound } from "next/navigation";
+import { locales, defaultLocale, type Locale } from "@aidir/core/i18n.config";
+
+/** 站点品牌 SEO 文案覆盖（每个网站不同） */
+const brandMessages = {
+  en: {
+    seo: { home: {"title":"AI Stack — Find the Best AI Tools, Ranked by Real Users","description":"The professional AI tools directory. 1,000+ AI tools across 14 categories ranked by community votes, reviews and engagement.","ogImage":"/og-image.png"} },
+    hero: { title: "AI Stack — Find the Best AI Tools, Ranked by Real Users", description: "The professional AI tools directory. 1,000+ AI tools across 14 categories ranked by community votes, reviews and engagement." },
+    common: { brand: { name: "AI Stack", tagline: "The professional AI tools directory — ranked by the community." } },
+  },
+  zh: {
+    seo: { home: {"title":"AI Stack — 由真实用户排名的 AI 工具目录","description":"专业 AI 工具导航：14 个分类、1000+ 工具，由社区投票、评论与互动数据实时排名。","ogImage":"/og-image.png"} },
+    hero: { title: "AI Stack — 由真实用户排名的 AI 工具目录", description: "专业 AI 工具导航：14 个分类、1000+ 工具，由社区投票、评论与互动数据实时排名。" },
+    common: { brand: { name: "AI Stack", tagline: "The professional AI tools directory — ranked by the community." } },
+  },
+} as const;
+
+export default getRequestConfig(async ({ requestLocale }) => {
+  let locale = await requestLocale;
+  if (!locale || !locales.includes(locale as Locale)) {
+    locale = defaultLocale;
+  }
+  try {
+    // 底座基础文案 + 站点品牌覆盖（浅合并到顶层命名空间）
+    const base = (await import(`../../messages/${locale}.json`)).default;
+    const override = brandMessages[locale as keyof typeof brandMessages];
+    const messages = { ...base };
+    for (const [ns, value] of Object.entries(override)) {
+      messages[ns] = { ...(messages[ns] ?? {}), ...value };
+    }
+    return { locale, messages };
+  } catch (error) {
+    console.error("Error loading messages for locale:", locale, error);
+    notFound();
+  }
+});