feat: recover portfolio pages from scratch workspaces

- Add base layouts (BaseLayout, BlogLayout, ProjectLayout)
- Add UI components (Header, Footer, Navigation, Card, Tag)
- Add About page with personal story
- Add Projects pages (index, detail)
- Add homepage content
- Add SEO files (robots.txt, webmanifest)

Work was done by agents in isolated workspaces.
Consolidated into main repo for proper git tracking.

src/pages/projects/[slug].astro

@@ -0,0 +1,21 @@
+---
+import { getCollection } from 'astro:content';
+import ProjectLayout from '../../layouts/ProjectLayout.astro';
+
+export async function getStaticPaths() {
+  const projects = await getCollection('projects');
+  return projects
+    .filter(p => !p.data.draft)
+    .map(project => ({
+      params: { slug: project.slug },
+      props: { project },
+    }));
+}
+
+const { project } = Astro.props;
+const { Content } = await project.render();
+---
+
+<ProjectLayout {...project.data}>
+  <Content />
+</ProjectLayout>