feat(customers): add initial admin bootstrap and csv import

frontend/athena/components/customers/ImportPreviewTable.tsx

@@ -0,0 +1,56 @@
+import type { CustomerImportPreviewRow } from "@/types/customer";
+
+const actionLabels = {
+  create: "Create",
+  update: "Update",
+  skip: "Skip",
+  error: "Error",
+};
+
+const actionClasses = {
+  create: "bg-emerald-50 text-emerald-700",
+  update: "bg-blue-50 text-blue-700",
+  skip: "bg-slate-100 text-slate-600",
+  error: "bg-red-50 text-red-700",
+};
+
+function issueText(row: CustomerImportPreviewRow) {
+  const issues = [...row.errors, ...row.warnings];
+  if (issues.length === 0) {
+    return "-";
+  }
+  return issues.map((issue) => `${issue.field || "Zeile"}: ${issue.message}`).join(" · ");
+}
+
+export default function ImportPreviewTable({ rows }: { rows: CustomerImportPreviewRow[] }) {
+  return (
+    <div className="max-h-80 overflow-auto rounded-lg border">
+      <table className="w-full min-w-[720px] border-collapse text-sm">
+        <thead className="sticky top-0 bg-slate-50 text-left text-xs uppercase text-slate-500">
+          <tr>
+            <th className="px-3 py-2">Zeile</th>
+            <th className="px-3 py-2">Aktion</th>
+            <th className="px-3 py-2">Kundennummer</th>
+            <th className="px-3 py-2">Firma</th>
+            <th className="px-3 py-2">Hinweise</th>
+          </tr>
+        </thead>
+        <tbody className="divide-y bg-white">
+          {rows.map((row) => (
+            <tr key={row.row}>
+              <td className="px-3 py-2 font-medium">{row.row}</td>
+              <td className="px-3 py-2">
+                <span className={`rounded-full px-2 py-1 text-xs font-semibold ${actionClasses[row.action]}`}>
+                  {actionLabels[row.action]}
+                </span>
+              </td>
+              <td className="px-3 py-2">{row.customer_number || "-"}</td>
+              <td className="px-3 py-2">{row.company_name || "-"}</td>
+              <td className="px-3 py-2 text-slate-600">{issueText(row)}</td>
+            </tr>
+          ))}
+        </tbody>
+      </table>
+    </div>
+  );
+}