feat(receipt-import): refactor product creation and category update to use server actions

frontend/app/kvitto/actions.ts

@@ -0,0 +1,41 @@
+'use server';
+
+import { getAuthHeaders } from '@/lib/auth-headers';
+
+const API_BASE = process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
+
+export async function createProductAction(name: string) {
+  const authHeaders = await getAuthHeaders();
+  console.log('[createProductAction] Creating product with name:', name);
+  console.log('[createProductAction] Auth headers:', authHeaders ? 'YES' : 'NO');
+
+  const res = await fetch(`${API_BASE}/api/products`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', ...authHeaders },
+    body: JSON.stringify({ name }),
+  });
+
+  if (!res.ok) {
+    const e = await res.json().catch(() => ({}));
+    throw new Error(e.message ?? `HTTP ${res.status}`);
+  }
+
+  return res.json();
+}
+
+export async function updateProductCategoryAction(productId: number, categoryId: number) {
+  const authHeaders = await getAuthHeaders();
+
+  const res = await fetch(`${API_BASE}/api/products/${productId}`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json', ...authHeaders },
+    body: JSON.stringify({ categoryId }),
+  });
+
+  if (!res.ok) {
+    const e = await res.json().catch(() => ({}));
+    throw new Error(e.message ?? `HTTP ${res.status}`);
+  }
+
+  return res.json();
+}