Skip UseFileServer when wwwroot is missing.

Local Aspire has no published client folder; the middleware warned on every boot.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Server/Program.cs

@@ -159,7 +159,11 @@ app.Map("/ws/game", async (HttpContext context, GameSocketHandler handler, Sessi
 app.MapDefaultEndpoints();
 
 // In a published container the built client lands in wwwroot next to the server.
-app.UseFileServer();
+// Local Aspire has no such folder — Vite serves the UI, and UseFileServer would warn.
+if (ClientStaticFiles.CanServe(app.Environment.WebRootPath))
+{
+    app.UseFileServer();
+}
 
 app.Run();