优化支付宝支付流程与 Web 端体验

- 支付宝新窗口跳转，轮询与手动刷新增加加载反馈
- 支付回跳先校验订单状态，避免未付款误报成功
- 门户登录回调统一，云文件打开加载与版本冲突同步
- 精简本地 start.bat 与 README 说明

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

frontend-web/assets/css/pay-sheet.css

@@ -454,19 +454,87 @@
 }
 
 .soon-pay-status {
-  margin: 0 0 12px;
+  margin: 0 0 8px;
   text-align: center;
   font-size: 12px;
   color: var(--soon-text-muted);
+  transition: color 0.2s ease, opacity 0.2s ease;
 }
 
 .soon-pay-status--ok { color: #4db6ac; }
 .soon-pay-status--err { color: var(--soon-danger); }
+.soon-pay-status--warn { color: #ffb74d; }
+
+.soon-pay-status.is-checking {
+  color: #4db6ac;
+  opacity: 0.85;
+}
+
+.soon-pay-poll {
+  display: none;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  margin: 0 0 10px;
+  font-size: 11px;
+  color: var(--soon-text-muted);
+}
+
+.soon-pay-sheet--polling .soon-pay-poll {
+  display: flex;
+}
+
+.soon-pay-poll__spin {
+  width: 12px;
+  height: 12px;
+  border: 2px solid rgba(255, 255, 255, 0.12);
+  border-top-color: #4db6ac;
+  border-radius: 50%;
+  animation: soon-pay-spin 0.75s linear infinite;
+  flex-shrink: 0;
+}
+
+.soon-pay-poll.is-tick .soon-pay-poll__spin {
+  animation-duration: 0.45s;
+}
+
+.soon-pay-sheet--polling .soon-pay-checkout-ready {
+  border-color: rgba(77, 182, 172, 0.28);
+  animation: soon-pay-wait-pulse 2.4s ease-in-out infinite;
+}
 
 .soon-pay-sheet__cta {
   width: 100%;
+  transition: opacity 0.2s ease;
 }
 
 .soon-pay-sheet__cta--secondary {
   margin-top: 8px;
 }
+
+.soon-pay-sheet__cta.is-loading {
+  opacity: 0.72;
+  pointer-events: none;
+}
+
+.soon-pay-sheet__cta.is-loading::before {
+  content: '';
+  display: inline-block;
+  width: 12px;
+  height: 12px;
+  margin-right: 6px;
+  vertical-align: -2px;
+  border: 2px solid rgba(255, 255, 255, 0.2);
+  border-top-color: currentColor;
+  border-radius: 50%;
+  animation: soon-pay-spin 0.75s linear infinite;
+}
+
+@keyframes soon-pay-spin {
+  to { transform: rotate(360deg); }
+}
+
+@keyframes soon-pay-wait-pulse {
+  0%, 100% { box-shadow: inset 0 0 0 0 rgba(77, 182, 172, 0); }
+  50% { box-shadow: inset 0 0 0 1px rgba(77, 182, 172, 0.22); }
+}