feat: proxy standalone domain landing pages for rspace.online/{moduleId}

Instead of the generated landing page, rspace.online/rnotes now fetches
and serves the real page from rnotes.online (with <base> tag for asset
resolution). 5-minute in-memory cache avoids repeated fetches. Falls
back to the generated landing page for modules without a standalone
domain or when the fetch fails.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/index.ts

@@ -98,6 +98,30 @@ const PORT = Number(process.env.PORT) || 3000;
 const INTERNAL_API_KEY = process.env.INTERNAL_API_KEY || "";
 const DIST_DIR = resolve(import.meta.dir, "../dist");
 
+// ── Standalone landing page proxy cache ──
+const landingCache = new Map<string, { html: string; at: number }>();
+const LANDING_TTL = 5 * 60 * 1000; // 5 minutes
+
+async function fetchStandaloneLanding(domain: string): Promise<string | null> {
+	const cached = landingCache.get(domain);
+	if (cached && Date.now() - cached.at < LANDING_TTL) return cached.html;
+
+	try {
+		const resp = await fetch(`https://${domain}/`, {
+			headers: { "Accept": "text/html" },
+			redirect: "follow",
+		});
+		if (!resp.ok) return null;
+		let html = await resp.text();
+		// Inject <base> so relative assets (CSS, JS, images) resolve to the standalone domain
+		html = html.replace(/<head([^>]*)>/i, `<head$1>\n<base href="https://${domain}/">`);
+		landingCache.set(domain, { html, at: Date.now() });
+		return html;
+	} catch {
+		return null;
+	}
+}
+
 // ── Hono app ──
 const app = new Hono();
 
@@ -780,7 +804,7 @@ const server = Bun.serve<WSData>({
 		}
 
 		// ── Bare-domain module routes: rspace.online/{moduleId} ──
-		// Exact module path → serve module landing page.
+		// Exact module path → proxy the standalone domain's landing page.
 		// Sub-paths (API, assets) → rewrite to /demo/{moduleId}/... for backward compat.
 		if (!subdomain && hostClean.includes("rspace.online")) {
 			const pathSegments = url.pathname.split("/").filter(Boolean);
@@ -788,8 +812,18 @@ const server = Bun.serve<WSData>({
 				const firstSegment = pathSegments[0];
 				const knownModuleIds = new Set(getAllModules().map((m) => m.id));
 				if (knownModuleIds.has(firstSegment)) {
-					// Exact module path → landing page
+					// Exact module path → proxy from standalone domain
 					if (pathSegments.length === 1) {
+						const mod = getAllModules().find((m) => m.id === firstSegment);
+						if (mod?.standaloneDomain) {
+							const html = await fetchStandaloneLanding(mod.standaloneDomain);
+							if (html) {
+								return new Response(html, {
+									headers: { "Content-Type": "text/html; charset=utf-8" },
+								});
+							}
+						}
+						// Fallback: generated landing page (no standalone domain or fetch failed)
 						const modInfo = getModuleInfoList().find((m) => m.id === firstSegment);
 						if (modInfo) {
 							return new Response(