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/components/app-shell.tsx

@@ -39,13 +39,13 @@ function CommandPalette({ open, onClose, navigate }: { open: boolean; onClose: (
   return createPortal(
     <div
       id="shell-command-bg"
-      className="show"
+      className="shell-command-bg show"
       aria-hidden="false"
       onClick={(event) => { if (event.target === event.currentTarget) onClose(); }}
     >
       <div className="shell-command" role="dialog" aria-modal="true" aria-label="命令面板">
-        <div className="shell-command-head">
-          <IconKitSvg name="search" />
+        <div className="shell-command-h">
+          <span className="ic"><IconKitSvg name="search" /></span>
           <input
             id="shell-command-input"
             autoFocus