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/Header.tsx

@@ -0,0 +1,20 @@
+import { Link } from "@tanstack/react-router";
+import Logo from "./Logo";
+
+export default function Header() {
+	return (
+		<header
+			id="nav-container"
+			className="fixed -top-1 w-full h-height-header z-50"
+		>
+			<div className="flex flex-row justify-between items-center h-full w-full max-w-max-section m-auto px-section-main-x">
+				<Link
+					to="/"
+					className="w-[120px] h-[120px] flex justify-center items-center rounded-3xl p-2 backdrop-blur-3xl"
+				>
+					<Logo />
+				</Link>
+			</div>
+		</header>
+	);
+}