feat(products): implement category selection and product creation in receipt import

frontend/app/api/products/route.ts

@@ -1,4 +1,5 @@
 import { NextRequest, NextResponse } from 'next/server';
+import { getAuthHeaders } from '../../../lib/auth-headers';
 
 const API_BASE = process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
 
@@ -10,7 +11,18 @@ export async function GET(req: NextRequest) {
   const res = await fetch(`${API_BASE}/api/products${query ? `?${query}` : ''}`, {
     cache: 'no-store',
   });
-
+  const data = await res.json();
+  return NextResponse.json(data, { status: res.status });
+}
+
+export async function POST(req: NextRequest) {
+  const authHeaders = await getAuthHeaders();
+  const body = await req.json();
+  const res = await fetch(`${API_BASE}/api/products`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', ...authHeaders },
+    body: JSON.stringify(body),
+  });
   const data = await res.json();
   return NextResponse.json(data, { status: res.status });
 }