fix(pay): 待支付浮窗无刷新同步

- modal-cache 失效时广播 aksrt:cache:invalidated
- 新增 GET /orders/wait-pay-float 返回浮窗片段
- wait-pay-float.js 监听 orders 标签失效并替换/移除浮窗、重启倒计时
- VIP/充值/下载待支付分支触发 orders 失效

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/js/core/modal-cache.js

@@ -73,6 +73,8 @@
         if (typeof flight.cancel === "function") flight.cancel();
       }
     });
+    // 广播失效标签，供页面常驻视图（如待支付浮窗）按标签自行刷新。
+    document.dispatchEvent(new CustomEvent("aksrt:cache:invalidated", { detail: { tags: wanted.slice() } }));
     return removed;
   }