feat(header): logo mark + Lee Teong Hoe in brand, two-row mobile nav

- brand: three-colour Hoelee mark (rasterised from the brand vector,
  transparent, public/images/hoelee-mark-96.png) followed by the name
- section links grouped in .nav-links so the mobile header puts them on
  their own row instead of wrapping past the search/lang/theme controls
- measured 320/360/390/414/600/768/1280: scrollWidth == innerWidth,
  header 91.6px two rows (<600px) / 60.3px one row, mark loads at 22/26px

src/layouts/BaseLayout.astro

@@ -176,11 +176,19 @@ const nav = isZh
   <body>
     <header class="site-header">
       <nav class="nav" aria-label="Main">
-        <a class="brand" href={isZh ? '/zh/' : '/'}>Mr<span class="dot"> Hoelee</span></a>
-        <a href={isZh ? '/zh/posts/' : '/posts/'}>{nav.posts}</a>
-        <a href={isZh ? '/zh/categories/' : '/categories/'}>{nav.categories}</a>
-        <a href={isZh ? '/zh/about/' : '/about/'}>{nav.about}</a>
-        <a href="/rss.xml" title={nav.rss}>{nav.rss}</a>
+        <a class="brand" href={isZh ? '/zh/' : '/'}>
+          <img class="brand-mark" src="/images/hoelee-mark-96.png" alt="" width="26" height="26" decoding="async" />
+          <span class="brand-name">{SITE.author}</span>
+        </a>
+        {/* Section links live in their own list so the mobile header can drop the
+            whole group onto a second row (`flex-basis: 100%`) instead of letting
+            individual links wrap around the search / language / theme controls. */}
+        <ul class="nav-links">
+          <li><a class="nav-link" href={isZh ? '/zh/posts/' : '/posts/'}>{nav.posts}</a></li>
+          <li><a class="nav-link" href={isZh ? '/zh/categories/' : '/categories/'}>{nav.categories}</a></li>
+          <li><a class="nav-link" href={isZh ? '/zh/about/' : '/about/'}>{nav.about}</a></li>
+          <li><a class="nav-link" href="/rss.xml" title={nav.rss}>{nav.rss}</a></li>
+        </ul>
         <button class="search-toggle" id="search-toggle" aria-label={isZh ? '搜索' : 'Search'}>
           ⌕ <span class="search-hint">{isZh ? '搜索' : 'Search'}</span><kbd class="search-key">/</kbd>
         </button>