feat: add pagination to blog listing (12 posts per page)

- Use Astro's paginate() with pageSize: 12
- Add prev/next navigation with page counter
- Generate /blog/, /blog/2/, /blog/3/ etc.

src/pages/blog.astro

@@ -2,12 +2,18 @@
 import PageShell from '../components/PageShell.astro';
 import { getCollection } from 'astro:content';
 
-const posts = (await getCollection('blog', ({ data }) => !data.draft)).sort(
-  (a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf(),
-);
+export async function getStaticPaths({ paginate }) {
+  const posts = (await getCollection('blog', ({ data }) => !data.draft)).sort(
+    (a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf(),
+  );
+
+  return paginate(posts, { pageSize: 12 });
+}
+
+const { page } = Astro.props;
 
 // Collect all unique categories
-const allCategories = [...new Set(posts.map((p) => p.data.category))].sort();
+const allCategories = [...new Set(page.data.map((p) => p.data.category))].sort();
 ---
 
 <PageShell
@@ -32,7 +38,7 @@ const allCategories = [...new Set(posts.map((p) => p.data.category))].sort();
     </div>
 
     <div class="blog-grid" id="blog-grid">
-      {posts.map((post) => {
+      {page.data.map((post) => {
         const fmt = new Intl.DateTimeFormat('th-TH', { day: '2-digit', month: 'short', year: '2-digit' }).format(post.data.pubDate);
         return (
           <a class="blog-card liquid-glass liquidGlass-wrapper" href={`/blog/${post.id}/`} data-cat={post.data.category}>
@@ -51,6 +57,31 @@ const allCategories = [...new Set(posts.map((p) => p.data.category))].sort();
     </div>
 
     <p class="blog-empty" id="blog-empty" hidden>ไม่พบบทความที่ตรงกับหมวดหมู่นี้</p>
+
+    <!-- Pagination -->
+    {page.lastPage > 1 && (
+      <nav class="blog-pagination" aria-label="หน้าบทความ">
+        {page.url.prev ? (
+          <a class="pagination-btn" href={page.url.prev} aria-label="หน้าก่อนหน้า">
+            ← ก่อนหน้า
+          </a>
+        ) : (
+          <span class="pagination-btn pagination-btn--disabled">← ก่อนหน้า</span>
+        )}
+
+        <span class="pagination-info">
+          หน้า {page.currentPage} จาก {page.lastPage}
+        </span>
+
+        {page.url.next ? (
+          <a class="pagination-btn" href={page.url.next} aria-label="หน้าถัดไป">
+            ถัดไป →
+          </a>
+        ) : (
+          <span class="pagination-btn pagination-btn--disabled">ถัดไป →</span>
+        )}
+      </nav>
+    )}
   </section>
 </PageShell>
 
@@ -143,6 +174,43 @@ const allCategories = [...new Set(posts.map((p) => p.data.category))].sort();
     padding: clamp(40px, 6vw, 80px) 0;
   }
 
+  /* Pagination */
+  .blog-pagination {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: 16px;
+    margin-top: clamp(32px, 4vw, 56px);
+    padding: 20px 0;
+  }
+  .pagination-btn {
+    display: inline-flex;
+    align-items: center;
+    gap: 6px;
+    padding: 10px 20px;
+    border-radius: 999px;
+    border: 1px solid var(--line);
+    background: rgb(255 255 255 / .60);
+    color: var(--ink);
+    font-size: 0.88rem;
+    font-weight: 700;
+    text-decoration: none;
+    transition: all .2s var(--ease);
+  }
+  .pagination-btn:hover {
+    background: var(--yellow);
+    border-color: var(--yellow);
+  }
+  .pagination-btn--disabled {
+    opacity: 0.4;
+    cursor: not-allowed;
+    pointer-events: none;
+  }
+  .pagination-info {
+    color: var(--muted);
+    font-size: 0.85rem;
+  }
+
   @media (max-width: 820px) {
     .blog-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
   }