feat(mui): first ui-kit wrappers (Button, Card, TextField) + barrel

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

src/admin/ui/Button.tsx

@@ -0,0 +1,6 @@
+import MuiButton, { type ButtonProps } from "@mui/material/Button";
+
+/** App Button: defaults to the brand primary contained style. */
+export default function Button(props: ButtonProps) {
+  return <MuiButton variant="contained" color="primary" {...props} />;
+}

src/admin/ui/Card.tsx

@@ -0,0 +1,10 @@
+import MuiCard, { type CardProps } from "@mui/material/Card";
+import CardContent from "@mui/material/CardContent";
+
+export default function Card({ children, ...props }: CardProps) {
+  return (
+    <MuiCard {...props}>
+      <CardContent>{children}</CardContent>
+    </MuiCard>
+  );
+}

src/admin/ui/TextField.tsx

@@ -0,0 +1,6 @@
+import MuiTextField, { type TextFieldProps } from "@mui/material/TextField";
+
+/** App TextField: small + outlined + full width by default. */
+export default function TextField(props: TextFieldProps) {
+  return <MuiTextField size="small" variant="outlined" fullWidth {...props} />;
+}

src/admin/ui/index.ts

@@ -0,0 +1,4 @@
+export { default as MuiProvider } from "./MuiProvider";
+export { default as Button } from "./Button";
+export { default as Card } from "./Card";
+export { default as TextField } from "./TextField";