fix: serve /admin directly in fetch handler to bypass /:space catch-all

Hono's parameterized /:space route was capturing /admin before the
explicit route. Move admin.html serving into the Bun.serve fetch
handler so it runs before Hono routing.

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

server/index.ts

@@ -524,6 +524,12 @@ const server = Bun.serve<WSData>({
 			return new Response("WebSocket upgrade failed", { status: 400 });
 		}
 
+		// ── Explicit page routes (before Hono, to avoid /:space catch-all) ──
+		if (url.pathname === "/admin") {
+			const adminHtml = await serveStatic("admin.html");
+			if (adminHtml) return adminHtml;
+		}
+
 		// ── Static assets (before Hono routing) ──
 		if (url.pathname !== "/" && !url.pathname.startsWith("/api/") && !url.pathname.startsWith("/ws/")) {
 			const assetPath = url.pathname.slice(1);