migrate from astro+netlify to tanstack start + self-hosted

Replace the Astro static site with a TanStack Start (Bun runtime) app and
add Dockerfile + compose files so the site can be served from home-main-2
behind the home-reverse-proxy-1 Caddy instead of Netlify. CI workflow
rewritten to build a container image and SSH-deploy to the home host.

src/components/LegalPage.tsx

@@ -0,0 +1,12 @@
+import type { FC, ReactNode } from "react";
+import Section from "./Section";
+
+const LegalPage: FC<{ children: ReactNode }> = ({ children }) => {
+	return (
+		<Section>
+			<article className="markdown">{children}</article>
+		</Section>
+	);
+};
+
+export default LegalPage;