fix(vip): 积分兑换弹窗改服务端渲染并与 Zibll 1:1 对齐

/user/vip/ 的积分兑换会员弹窗原先是前端自行拼装的，结构与层级都与参考主题
Zibll 不一致：Zibll 走 zibpay_get_vip_points_exchange_modal() 服务端渲染静态
壳，前端只按需开合。改为同一模型，前端不再拼 HTML。

- VipServiceModal 新增 get_points_exchange_modal_html()：门控（未登录/未开启
  返回空串）、vip-card 套餐选择、积分不足提示与提交表单；wp_footer 挂载输出
- pay-vip.js 移除 renderPointsModal / pointsPackage / exchangeFromModal /
  vipPointsPay，改为自包含开合（.in + 内联 display:flex + 独立遮罩 +
  body.modal-open + ESC），保留 aksrt-vip-points-toast 的 load/success/danger 契约
- 移除 /user/vip/ 页面底部独立积分兑换入口及其样式（uc-vip-points-link）
- credits.js 清理依赖全站不存在选择器的死代码 initVipPointsExchange()
- vip-modal.css 删除 71 行自实现样式，改为 .modal[data-aksrt-vip-points-modal]
  显隐契约；层级 100050 < 遮罩 100055 < 弹窗 100060 < notyf 10000000
- 新增 vip-points-exchange-modal 契约测试（7 项），toast-contract 同步

静止态必须显式 display:none，否则 .flex{display:flex} 会覆盖 .modal{display:none}
形成隐形遮罩拦截整页点击。

未写数据迁移。

验证：node --test tests/widget-system/*.test.cjs 308 项全部通过；php -l 全部
改动文件通过；隔离渲染桩确认积分充足 / 积分不足 / 功能关闭 / 未登录四种情形
的 HTML 产物正确。

assets/css/routes/user-center/credits.css

@@ -1331,70 +1331,6 @@ body.uc-modal-open {
   margin: 0 !important;
   line-height: 1;
 }
-.uc-vip-points-link {
-  display: flex;
-  align-items: center;
-  gap: 14px;
-  min-width: 0;
-  margin-top: 12px;
-  padding: 14px 16px;
-  border: 1px solid rgba(16, 185, 129, 0.24);
-  border-radius: 12px;
-  background: linear-gradient(105deg, rgba(16, 185, 129, 0.1), var(--surface-1, #fff) 62%);
-  box-shadow: 0 6px 18px rgba(16, 185, 129, 0.08);
-}
-.uc-vip-points-link__icon {
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  width: 40px;
-  height: 40px;
-  flex: 0 0 40px;
-  border-radius: 12px;
-  color: #047857;
-  background: rgba(16, 185, 129, 0.15);
-  font-size: 18px;
-}
-.uc-vip-points-link__body {
-  display: flex;
-  flex: 1 1 auto;
-  min-width: 0;
-  flex-direction: column;
-  gap: 3px;
-}
-.uc-vip-points-link__body strong { font-size: 14px; }
-.uc-vip-points-link__body span {
-  overflow: hidden;
-  color: var(--color-ink-3, #6b7280);
-  font-size: 12px;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-.uc-vip-points-link__action {
-  display: inline-flex;
-  align-items: center;
-  gap: 7px;
-  flex: 0 0 auto;
-  min-height: 34px;
-  padding: 0 13px;
-  border: 0;
-  border-radius: 999px;
-  color: #047857;
-  background: rgba(16, 185, 129, 0.12);
-  cursor: pointer;
-  font: inherit;
-  font-size: 13px;
-  font-weight: 700;
-}
-.uc-vip-points-link__action:hover { background: rgba(16, 185, 129, 0.2); }
-.uc-vip-points-link__action:focus-visible,
-.uc-vip-points-link:focus-within { outline: 3px solid rgba(16, 185, 129, 0.3); outline-offset: 2px; }
-@media (max-width: 480px) {
-  .uc-vip-points-link { align-items: flex-start; flex-wrap: wrap; }
-  .uc-vip-points-link__body { flex-basis: calc(100% - 54px); }
-  .uc-vip-points-link__action { margin-left: 54px; }
-}
-
 .uc-vip-assets-entry {
   gap: 12px;
 }