feat(core): notification inbox infinite scroll + command palette fix (+ pending WIP)

消息中心:全量渲染 → 真·后端分页滚动加载
- backend(ops/views): NotificationPagination(10/页,page_size 可覆盖)+
  响应回 type_counts(按收件人绝对计数,不受分页/搜索影响)
- frontend(messages): 自管分页,滚到底加载下一批;tab/搜索走服务端并重置到第1页;
  代号作废在途旧请求防切换卡空白;乐观标已读;「已加载 X / Y」分母用当前筛选总数
- api/App/types: listNotifications 支持 page/page_size/search;allNotifications 携带 type_counts

命令面板(侧边栏搜索):修复点开后 UI 错位
- app-shell: 遮罩 className 漏了基类 shell-command-bg(只有 .show)致无定位塌到左下;
  补回基类 + header 类名对齐 .shell-command-h
- messages-page.css: 工作台收进视口高度,收件箱在面板内滚动

本次提交一并带入此前若干未提交 WIP(account/ai-tools/library/pipeline/products/settings +
accounts/ai/assets/billing/projects 后端),按用户要求整体推 dev。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/frontend/src/product-create-page.css

@@ -385,6 +385,10 @@
   background: repeating-linear-gradient(135deg, transparent 0 6px, rgba(0,0,0,.03) 6px 7px);
   pointer-events: none;
 }
+/* 真实示例图:图片铺满,去掉斜纹底 */
+.pc-drawer .form-card .pf-example .ex-grid .ex-thumb--img { background: var(--background-lighter); }
+.pc-drawer .form-card .pf-example .ex-grid .ex-thumb--img::after { display: none; }
+.pc-drawer .form-card .pf-example .ex-grid .ex-thumb--img img { width: 100%; height: 100%; object-fit: cover; display: block; }
 .pc-drawer .form-card .pf-example .ex-d {
   font-size: 12px; color: var(--black-alpha-56); line-height: 1.5;
 }