feat: add blog with archives, pagination, search, sharing and RSS

- Content collection (one folder per post) with zod schema
- /blog, category and tag archives with /sayfa/<n>/ pagination
- Post page: breadcrumbs, date badges, share bar, TOC, DIY notice,
  code copy, license line, prev/next, BlogPosting + BreadcrumbList JSON-LD
- Sidebar: Pagefind search, categories, featured fallback, tag cloud
- Sätteri HAST plugins for figure/figcaption and external links
- Dual-theme Shiki, themed prose, RSS feed, latest posts on home
- Three sample posts marked as examples

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/styles/global.css

@@ -120,3 +120,100 @@
     scroll-behavior: auto !important;
   }
 }
+
+/* ---------- Article typography (unlayered: overrides the typography plugin) ---------- */
+.article-prose {
+  --tw-prose-body: var(--fg);
+  --tw-prose-headings: var(--fg);
+  --tw-prose-lead: var(--fg-muted);
+  --tw-prose-links: var(--accent-strong);
+  --tw-prose-bold: var(--fg);
+  --tw-prose-counters: var(--fg-muted);
+  --tw-prose-bullets: var(--accent);
+  --tw-prose-hr: var(--line);
+  --tw-prose-quotes: var(--fg);
+  --tw-prose-quote-borders: var(--accent);
+  --tw-prose-captions: var(--fg-muted);
+  --tw-prose-kbd: var(--fg);
+  --tw-prose-code: var(--fg);
+  --tw-prose-pre-code: var(--fg);
+  --tw-prose-pre-bg: var(--surface);
+  --tw-prose-th-borders: var(--fg);
+  --tw-prose-td-borders: var(--line);
+}
+
+.article-prose :where(h2, h3, h4) {
+  font-family: var(--font-display);
+  font-weight: 800;
+  scroll-margin-top: 2rem;
+}
+
+.article-prose :where(a) {
+  text-decoration-thickness: 2px;
+  text-underline-offset: 0.2em;
+}
+
+.article-prose :where(:not(pre) > code) {
+  background: var(--bg-alt);
+  padding: 0.1em 0.35em;
+  border-radius: 2px;
+  font-weight: 500;
+}
+.article-prose :where(:not(pre) > code)::before,
+.article-prose :where(:not(pre) > code)::after {
+  content: none;
+}
+
+.article-prose :where(blockquote) {
+  font-style: normal;
+  background: var(--surface);
+  padding-block: 0.25em;
+}
+.article-prose :where(blockquote p)::before,
+.article-prose :where(blockquote p)::after {
+  content: none;
+}
+
+.article-prose :where(figure) {
+  margin-inline: 0;
+}
+.article-prose :where(figcaption) {
+  border-left: 3px solid var(--accent);
+  padding-left: 0.75em;
+}
+
+/* Shiki dual theme (defaultColor: false) */
+.astro-code {
+  color: var(--shiki-light);
+  background-color: var(--surface) !important;
+  border: 1px solid var(--line);
+  border-radius: 2px;
+}
+.astro-code span {
+  color: var(--shiki-light);
+}
+[data-theme='dark'] .astro-code,
+[data-theme='dark'] .astro-code span {
+  color: var(--shiki-dark);
+}
+
+.code-block {
+  position: relative;
+}
+.code-copy {
+  position: absolute;
+  top: 0.5rem;
+  right: 0.5rem;
+  padding: 0.15rem 0.6rem;
+  font: 700 0.75rem/1.5 var(--font-display);
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+  color: var(--bg);
+  background: var(--fg);
+  border-radius: 2px;
+  cursor: pointer;
+}
+.code-copy:hover {
+  background: var(--accent-fill);
+  color: var(--on-accent-fill);
+}