feat(mui): kit primitives — PageHeader, EmptyState, LoadingState, FilterBar, StatCard + DataTable onRowClick/rowDanger

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

src/admin/ui/PageHeader.tsx

@@ -0,0 +1,48 @@
+import type { ReactNode } from "react";
+import Box from "@mui/material/Box";
+import Typography from "@mui/material/Typography";
+
+export interface PageHeaderProps {
+  title: string;
+  subtitle?: string;
+  actions?: ReactNode;
+}
+
+/**
+ * Standard page header: title (+ optional subtitle) on the left,
+ * action controls on the right. No framer-motion — pages add their own entrance.
+ */
+export default function PageHeader({
+  title,
+  subtitle,
+  actions,
+}: PageHeaderProps) {
+  return (
+    <Box
+      sx={{
+        display: "flex",
+        alignItems: "flex-start",
+        justifyContent: "space-between",
+        flexWrap: "wrap",
+        gap: 2,
+        mb: 3,
+      }}
+    >
+      <Box>
+        <Typography variant="h4">{title}</Typography>
+        {subtitle && (
+          <Typography variant="body2" color="text.secondary" sx={{ mt: 0.5 }}>
+            {subtitle}
+          </Typography>
+        )}
+      </Box>
+      {actions && (
+        <Box
+          sx={{ display: "flex", alignItems: "center", gap: 1, flexShrink: 0 }}
+        >
+          {actions}
+        </Box>
+      )}
+    </Box>
+  );
+}