fix: 房间加载失败时显示具体错误原因，便于线上排查

src/app/blindbox/page.tsx

@@ -179,7 +179,7 @@ export default function BlindboxLobbyPage() {
   const [creating, setCreating] = useState(false);
   const [joining, setJoining] = useState(false);
   const [error, setError] = useState("");
-  const [loadError, setLoadError] = useState(false);
+  const [loadError, setLoadError] = useState<string | false>(false);
 
   const [confirmDeleteId, setConfirmDeleteId] = useState<string | null>(null);
   const [deletingId, setDeletingId] = useState<string | null>(null);
@@ -193,12 +193,15 @@ export default function BlindboxLobbyPage() {
     }
     try {
       const res = await fetch(`/api/blindbox/rooms?userId=${p.id}`, { cache: "no-store" });
-      if (!res.ok) throw new Error();
+      if (!res.ok) {
+        const body = await res.json().catch(() => null);
+        throw new Error(body?.error ?? `HTTP ${res.status}`);
+      }
       const data = await res.json();
       setRooms(Array.isArray(data.rooms) ? data.rooms : []);
       setLoadError(false);
-    } catch {
+    } catch (e) {
-      if (!silent) setLoadError(true);
+      if (!silent) setLoadError(e instanceof Error ? e.message : "未知错误");
     } finally {
       if (!silent) setLoading(false);
     }
@@ -434,6 +437,9 @@ export default function BlindboxLobbyPage() {
           >
             <Package size={36} className="text-purple-400/30" strokeWidth={1.5} />
             <p className="text-sm text-muted">加载房间失败</p>
+            {typeof loadError === "string" && (
+              <p className="max-w-xs text-center text-[11px] text-muted/60 break-all">{loadError}</p>
+            )}
             <button
               onClick={() => fetchRooms()}
               className="mt-1 text-xs font-medium text-purple-400 active:text-purple-300"