feat(mui): kit — DateField over MUI X (date-fns v4, cs locale) + LocalizationProvider

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/ui/index.ts

@@ -15,3 +15,4 @@ export { default as Alert } from "./Alert";
 export { Tabs, TabPanel } from "./Tabs";
 export type { TabDef } from "./Tabs";
 export { default as Pagination } from "./Pagination";
+export { default as DateField } from "./DateField";