feat: init Astro blog with wikilinks, KaTeX and local search

- Astro 5 static blog, zero runtime JS
- Obsidian wikilink remark plugin (slug matches Astro content collection)
- KaTeX math rendering, local search, TOC, archives, tags
- 5 posts on math/physics/ML topics
- deploy scripts for nginx + certbot + rsync

src/pages/posts/index.astro

@@ -0,0 +1,42 @@
+---
+import BaseLayout from '../../layouts/BaseLayout.astro';
+import PostCard from '../../components/PostCard.astro';
+import TagChip from '../../components/TagChip.astro';
+import { getPublishedPosts, getAllTags } from '../../lib/utils';
+
+const all = await getPublishedPosts();
+const tags = getAllTags(all);
+---
+
+<BaseLayout title="全部文章" description="Yukun's Blog 的全部文章列表">
+  <section class="container" style="padding-top: calc(var(--nav-h) + 48px);">
+    <header class="page-head reveal">
+      <h1 class="page-title">全部文章</h1>
+      <p class="page-sub">共 {all.length} 篇 · 按发布时间倒序排列</p>
+    </header>
+
+    <div class="tag-bar glass reveal">
+      <span class="tag-label">筛选标签</span>
+      <div class="tag-list">
+        <a href="/posts" class="tag-chip active">全部</a>
+        {tags.map((t) => <TagChip tag={t.tag} count={t.count} />)}
+      </div>
+    </div>
+  </section>
+
+  <section class="container section" style="padding-top: 24px;">
+    <div class="post-grid">
+      {all.map((post) => <PostCard post={post} class="reveal" />)}
+    </div>
+  </section>
+</BaseLayout>
+
+<style>
+  .page-head { margin-bottom: 28px; }
+  .page-title { font-family: var(--font-display); font-weight: 800; font-size: clamp(2rem, 1rem + 4vw, 3rem); letter-spacing: -0.03em; color: var(--ink); }
+  .page-sub { color: var(--ink-soft); margin-top: 8px; }
+  .tag-bar { border-radius: var(--r-lg); padding: 14px 18px; display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
+  .tag-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--ink-faint); font-weight: 700; white-space: nowrap; }
+  .tag-list { display: flex; flex-wrap: wrap; gap: 8px; }
+  .post-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: clamp(16px, 2.5vw, 24px); }
+</style>