polish(admin): 抽出后台控件包并统一各页布局与交互

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

frontend/components/admin/index.ts

@@ -0,0 +1,13 @@
+export { default as AdminPageHeader } from "./AdminPageHeader";
+export { default as AdminSection } from "./AdminSection";
+export { default as AdminSwitch } from "./AdminSwitch";
+export { default as AdminSettingRow } from "./AdminSettingRow";
+export { default as AdminSegmented } from "./AdminSegmented";
+export type { AdminSegmentOption } from "./AdminSegmented";
+export { default as AdminSearchField } from "./AdminSearchField";
+export { default as AdminPager } from "./AdminPager";
+export { default as AdminEmpty } from "./AdminEmpty";
+export { default as AdminStatCard } from "./AdminStatCard";
+export { default as AdminIconButton } from "./AdminIconButton";
+export { default as AdminStatusChip, contentStatusChip } from "./AdminStatusChip";
+export type { AdminStatusTone } from "./AdminStatusChip";