feat: design-system upgrade + brand to 'Mr Hoelee'

- Extract CSS into src/styles/global.css with design tokens (hoelee.com brand palette)
- Self-hosted Inter + JetBrains Mono via @fontsource
- Sticky nav + manual light/dark toggle + copy-button code blocks
- Author card + Person JSON-LD (E-E-A-T), article meta, related posts, reading time
- Full SEO: canonical, OG (with dims), twitter:card, favicon (all sizes), RSS + sitemap
- New /categories/ and /categories/[category]/ pages
- Add docs/ knowledge guides (content, design, seo, ops) + README index
- Brand name: hoelee.dev -> Mr Hoelee

src/components/AuthorCard.astro

@@ -0,0 +1,23 @@
+---
+import { SITE } from '../config';
+
+interface Props {
+  bio?: string;
+}
+
+const { bio = 'Full-stack developer & DevOps engineer. I build web apps, self-host infrastructure, and automate things — this blog is my living portfolio.' } = Astro.props;
+---
+
+<div class="author-card">
+  <div class="avatar" aria-hidden="true">{SITE.handle.charAt(0)}</div>
+  <div>
+    <p class="who">{SITE.author}</p>
+    <p class="bio">{bio}</p>
+    <div class="links">
+      <a href={SITE.linkedin} target="_blank" rel="noopener">LinkedIn</a>
+      <a href={SITE.github} target="_blank" rel="noopener">GitHub</a>
+      <a href={SITE.gitea} target="_blank" rel="noopener">Gitea</a>
+      <a href={SITE.website} target="_blank" rel="noopener">hoelee.com</a>
+    </div>
+  </div>
+</div>

src/components/PostList.astro

@@ -0,0 +1,29 @@
+---
+import type { CollectionEntry } from 'astro:content';
+
+interface Props {
+  posts: CollectionEntry<'posts'>[];
+  limit?: number;
+}
+
+const { posts, limit } = Astro.props;
+const shown = limit ? posts.slice(0, limit) : posts;
+
+const fmt = (d: Date) =>
+  d.toLocaleDateString('en-US', { year: 'numeric', month: 'long', day: 'numeric' });
+---
+
+<ul class="post-list">
+  {shown.map((post) => (
+    <li>
+      <a href={`/posts/${post.slug}/`}><h2>{post.data.title}</h2></a>
+      <div class="meta">
+        <time datetime={post.data.pubDate.toISOString()}>{fmt(post.data.pubDate)}</time>
+        <span class="sep">·</span>
+        <a class="tag" href={`/categories/${post.data.category}/`}>{post.data.category}</a>
+        {post.data.tags.map((t) => <span class="tag">{t}</span>)}
+      </div>
+      <p>{post.data.description}</p>
+    </li>
+  ))}
+</ul>