refactor(download): open generated links directly without the popup

The success modal added a second click between the download button and
the file: request -> "下载链接已生成" popup -> 立即下载. Drop it and open
the generated relay link right away, keeping the previous new-tab
behaviour; a missing link still surfaces the error view.

- Replace renderSuccess with startDownload (anchor + target=_blank)
- Remove the popup-only CSS: alert, code-row, copy button, chips, meta
  and the download action skin; error, cashier and scan-pay views keep
  their styles

assets/css/frontend/cms-download.css

@@ -192,20 +192,6 @@
   line-height: 1.65;
 }
 
-.aksrt-dl-modal__alert {
-  margin: 0 0 14px;
-  padding: 11px 13px;
-  font-size: 13px;
-  line-height: 1.6;
-  border-radius: var(--radius, 8px);
-}
-
-.aksrt-dl-modal__alert--warn {
-  color: var(--color-warning-text, #ad6800);
-  background: var(--color-warning-bg, #fffbe6);
-  border: 1px solid #fde68a;
-}
-
 /* 提取码卡片 */
 .aksrt-dl-modal__code-card {
   padding: 13px 15px;
@@ -223,14 +209,6 @@
   letter-spacing: 0.08em;
 }
 
-.aksrt-dl-modal__code-row {
-  display: flex;
-  gap: 10px;
-  align-items: center;
-  justify-content: space-between;
-  min-width: 0;
-}
-
 .aksrt-dl-modal__code {
   display: block;
   min-width: 0;
@@ -250,64 +228,6 @@
   white-space: normal;
 }
 
-.aksrt-dl-modal__copy {
-  appearance: none;
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  flex: 0 0 auto;
-  height: 30px;
-  padding: 0 14px;
-  color: var(--focus-color, #f04494);
-  font-family: inherit;
-  font-size: 12px;
-  font-weight: 700;
-  line-height: 1;
-  background: var(--focus-color-opacity1, rgba(240, 68, 148, 0.1));
-  border: 0;
-  border-radius: 999px;
-  cursor: pointer;
-}
-
-.aksrt-dl-modal__copy:hover {
-  background: var(--focus-color-opacity3, rgba(240, 68, 148, 0.3));
-}
-
-.aksrt-dl-modal__copy:focus-visible {
-  outline: 2px solid var(--focus-color, #f04494);
-  outline-offset: 1px;
-}
-
-.aksrt-dl-modal__copy.is-done {
-  color: var(--color-success, #10b981);
-  background: var(--aksrt-green-soft, rgba(16, 185, 129, 0.12));
-}
-
-/* 信息 chips 行 */
-.aksrt-dl-modal__meta {
-  display: flex;
-  flex-wrap: wrap;
-  gap: 8px;
-  margin: 0 0 16px;
-}
-
-.aksrt-dl-modal__chip {
-  display: inline-flex;
-  gap: 6px;
-  align-items: center;
-  padding: 5px 11px;
-  color: var(--muted-color, #777);
-  font-size: 12px;
-  font-weight: 600;
-  background: var(--surface-2, rgba(0, 0, 0, 0.04));
-  border-radius: 999px;
-}
-
-.aksrt-dl-modal__chip i {
-  color: var(--focus-color, #f04494);
-  font-size: 12px;
-}
-
 /* 操作按钮 */
 .aksrt-dl-modal__actions {
   display: flex;
@@ -352,16 +272,6 @@
   outline-offset: 2px;
 }
 
-.aksrt-dl-modal__download {
-  min-height: 48px;
-  font-size: 15px;
-  box-shadow: 0 10px 20px -8px rgba(var(--color-primary-rgb, 240, 68, 148), 0.55);
-}
-
-.aksrt-dl-modal__download:hover {
-  box-shadow: 0 12px 24px -8px rgba(var(--color-primary-rgb, 240, 68, 148), 0.65);
-}
-
 /* ============================================================
  * 收银台（参考实现契约结构）
  * ============================================================ */
@@ -845,11 +755,6 @@ body.aksrt-dl-modal-open {
   .aksrt-dl-modal__code {
     font-size: 18px;
   }
-
-  .aksrt-dl-modal__chip {
-    padding: 4px 10px;
-    font-size: 11.5px;
-  }
 }
 
 @media (prefers-reduced-motion: reduce) {