feat(site): migrate from Next.js to Astro

Replace Next.js 16 + React 19 with Astro 5. Same visual design,
same deploy pipeline, zero client-side framework.

- All components rewritten as .astro files
- Dark mode via inline scripts (no React context)
- Timeline animation via IntersectionObserver script
- Nav active state computed at build time
- Self-hosted Source Code Pro woff2 fonts
- Drop Font Awesome (icons were never loaded)
- Drop unused headshot PNG (1MB, unreferenced)
- Fix pfSense hardware refs (Netgate 1100, not N100)
- Output: 212KB static HTML vs 2.6MB before
- JS shipped: ~700 bytes inline vs ~130KB React runtime

src/data/projects.ts

@@ -27,8 +27,8 @@ export const projects: Project[] = [
     slug: "portfolio",
     title: "portfolio",
     description:
-      "Next.js 16 static site, self-hosted in a DMZ LXC behind Nginx, deployed via Gitea Actions CI.",
-    tags: ["Next.js", "Dockerfile", "Tailwind", "nginx", "Caddy"],
+      "Astro static site, self-hosted in a DMZ LXC behind Nginx, deployed via Gitea Actions CI.",
+    tags: ["Astro", "Dockerfile", "Tailwind", "nginx", "Caddy"],
     githubUrl: "https://gitea.lerkolabs.com/lerko/portfolio",
     tier: "featured",
     year: 2021,