chore: bind website dev/preview server to IPv4 loopback (127.0.0.1)

Astro/Vite's default localhost bind resolves to IPv6 ::1 on this host,
which silently breaks `ssh -L 4321:127.0.0.1:4321` tunnels (they target
IPv4). Pin server.host to 127.0.0.1 so dev/preview is reachable over an
IPv4 loopback forward. Loopback-only — no network exposure.

website/astro.config.mjs

@@ -8,6 +8,11 @@ import tailwindcss from '@tailwindcss/vite';
 export default defineConfig({
 	// TODO(Phase B/SEO): set `site` to the production URL once the domain is
 	// known — enables the sitemap and canonical/OG URLs.
+	// Bind the dev/preview server to IPv4 loopback. Astro/Vite's default
+	// `localhost` bind resolves to IPv6 `::1` here, which breaks SSH
+	// `-L 4321:127.0.0.1:4321` tunnels (they target IPv4). Pinning 127.0.0.1
+	// keeps loopback-only access and makes tunnelling unambiguous.
+	server: { host: '127.0.0.1' },
 	integrations: [
 		starlight({
 			title: 'RDBMS Playground',