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

astro.config.mjs

@@ -0,0 +1,10 @@
+import { defineConfig } from 'astro/config';
+
+export default defineConfig({
+  output: 'static',
+  trailingSlash: 'always',
+  outDir: 'out',
+  build: {
+    format: 'directory',
+  },
+});