feat(ai): implement AI models management and configuration in admin panel

frontend/app/api/ai-config/route.ts

@@ -0,0 +1,15 @@
+import { NextResponse } from 'next/server';
+import { auth } from '../../../auth';
+
+export async function GET() {
+  const session = await auth();
+  if ((session?.user as any)?.role !== 'admin') {
+    return NextResponse.json({ error: 'Forbidden' }, { status: 403 });
+  }
+
+  const key = process.env.MISTRAL_API_KEY ?? '';
+  const keyHint = key.length >= 4 ? key.slice(-4) : '????';
+  const hasKey = key.length > 0;
+
+  return NextResponse.json({ keyHint, hasKey });
+}