feat(pay): add wait-pay float window aligned with reference theme

- Render pending orders (max 5, >=3 min left) in a top-right float button
  with hover list and countdown, gated by pay_wait_float_s
- Fix order countdown parsing expires_at as UTC
- Drop unused .paid-modal-lists-box thumb rule

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

assets/css/frontend/floating-buttons.css

@@ -176,8 +176,61 @@ body:has(.modal.in) .float-right.position-center,
     }
 }
 
+/* 待支付订单浮窗（对齐参考主题 .float-right-wait-pay） */
+.float-right.position-top {
+    bottom: auto;
+    top: 80px;
+}
+
+.float-btn.wait-pay-btn .hover-show-con {
+    animation: float-wait-pay 2s;
+    animation-delay: 0.3s;
+}
+
+body.modal-open .float-btn.wait-pay-btn .hover-show-con {
+    opacity: 0 !important;
+}
+
+.float-btn .order-thumb {
+    width: 48px;
+    height: 48px;
+}
+
+.float-btn .order-item {
+    color: inherit;
+}
+
+@keyframes float-wait-pay {
+    0% {
+        opacity: 0;
+        visibility: unset;
+        box-shadow: 0 0 10px 0 rgba(255, 73, 121, 0.1);
+    }
+    10% {
+        opacity: 1;
+        box-shadow: 0 0 10px 0 rgba(255, 73, 121, 0.95);
+    }
+    30% {
+        box-shadow: 0 0 10px 0 rgba(255, 73, 121, 0.1);
+    }
+    50% {
+        box-shadow: 0 0 10px 0 rgba(255, 73, 121, 0.95);
+    }
+    70% {
+        box-shadow: 0 0 10px 0 rgba(255, 73, 121, 0.1);
+    }
+    80% {
+        visibility: unset;
+        opacity: 1;
+    }
+}
+
 @media (max-width: 640px) {
     .float-right {
         right: 10px;
     }
+
+    .float-right.position-top {
+        top: 56px;
+    }
 }