fix: restore @ts-expect-error for request.ip in getClientIp

The property was removed from NextRequest types in Next.js 15+ but is
still populated by hosting platforms (Vercel, Netlify, etc.).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/rate-limit.ts

@@ -14,7 +14,8 @@ import { getConfig } from './config';
 
 export function getClientIp(request: NextRequest): string {
   const config = getConfig();
-  const directIp = request.ip; // Populated by Next.js if on Vercel/Netlify
+  // @ts-expect-error - Next.js 15+ removed request.ip from types but hosting platforms still populate it
+  const directIp = request.ip as string | undefined;
 
   const xForwardedFor = request.headers.get('x-forwarded-for');
   const xRealIp = request.headers.get('x-real-ip');