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.

public/robots.txt

@@ -0,0 +1,8 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://davidaragon.impresion3d.pro/sitemap-index.xml
+
+# Disallow admin/private areas (if any)
+Disallow: /admin/
+Disallow: /api/