feat: add receipt import functionality with UI and backend integration

frontend/app/api/receipt-import-proxy/route.ts

@@ -0,0 +1,19 @@
+import { NextRequest, NextResponse } from 'next/server';
+
+const API_BASE =
+  process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
+
+export async function POST(request: NextRequest) {
+  const formData = await request.formData();
+
+  const res = await fetch(`${API_BASE}/api/receipt-import`, {
+    method: 'POST',
+    body: formData,
+  });
+
+  const text = await res.text();
+  return new NextResponse(text, {
+    status: res.status,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}