feat: 重构博客为水墨纸质风格 + 搭建后台管理系统

- 重新设计全站 UI：parchment/ink/terracotta 水墨纸质色系，宋式 serif 排版
- 新增页面：文章列表、文章详情、分类、标签、关于
- GSAP ScrollTrigger 滚动动画 + 逐字揭示效果
- 后台管理系统 /admin：文章/分类/标签 CRUD，JSON 文件存储
- 登录认证（cookie session）
- 设计系统文档 UI.md

src/app/page.tsx

@@ -1,65 +1,16 @@
-import Image from "next/image";
+import { posts } from "@/data/posts";
+import HeroSection from "@/components/HeroSection";
+import { FeaturedGrid, RecentList } from "@/components/PostSections";
+
+export default function HomePage() {
+  const featuredPosts = posts.filter((p) => p.featured);
+  const recentPosts = posts.slice(0, 5);
 
-export default function Home() {
   return (
-    <div className="flex flex-col flex-1 items-center justify-center bg-zinc-50 font-sans dark:bg-black">
-      <main className="flex flex-1 w-full max-w-3xl flex-col items-center justify-between py-32 px-16 bg-white dark:bg-black sm:items-start">
-        <Image
-          className="dark:invert"
-          src="/next.svg"
-          alt="Next.js logo"
-          width={100}
-          height={20}
-          priority
-        />
-        <div className="flex flex-col items-center gap-6 text-center sm:items-start sm:text-left">
-          <h1 className="max-w-xs text-3xl font-semibold leading-10 tracking-tight text-black dark:text-zinc-50">
-            To get started, edit the page.tsx file.
-          </h1>
-          <p className="max-w-md text-lg leading-8 text-zinc-600 dark:text-zinc-400">
-            Looking for a starting point or more instructions? Head over to{" "}
-            <a
-              href="https://vercel.com/templates?framework=next.js&utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Templates
-            </a>{" "}
-            or the{" "}
-            <a
-              href="https://nextjs.org/learn?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Learning
-            </a>{" "}
-            center.
-          </p>
-        </div>
-        <div className="flex flex-col gap-4 text-base font-medium sm:flex-row">
-          <a
-            className="flex h-12 w-full items-center justify-center gap-2 rounded-full bg-foreground px-5 text-background transition-colors hover:bg-[#383838] dark:hover:bg-[#ccc] md:w-[158px]"
-            href="https://vercel.com/new?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            <Image
-              className="dark:invert"
-              src="/vercel.svg"
-              alt="Vercel logomark"
-              width={16}
-              height={16}
-            />
-            Deploy Now
-          </a>
-          <a
-            className="flex h-12 w-full items-center justify-center rounded-full border border-solid border-black/[.08] px-5 transition-colors hover:border-transparent hover:bg-black/[.04] dark:border-white/[.145] dark:hover:bg-[#1a1a1a] md:w-[158px]"
-            href="https://nextjs.org/docs?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            Documentation
-          </a>
-        </div>
-      </main>
-    </div>
+    <>
+      <HeroSection />
+      <FeaturedGrid posts={featuredPosts} />
+      <RecentList posts={recentPosts} />
+    </>
   );
 }