feat(product): implement updateProductWithTags function for updating product and tags

frontend/app/admin/products/EditProductForm.tsx

@@ -2,7 +2,7 @@
 
 import { useState, useTransition, useEffect } from 'react';
 import type { Product } from '../../../features/inventory/types';
-import { updateProduct, deleteProduct, setProductTags, suggestProductCategory } from './actions';
+import { updateProductWithTags, deleteProduct, suggestProductCategory } from './actions';
 
 type CategoryNode = {
   id: number;
@@ -104,8 +104,7 @@ export default function EditProductForm({ product }: Props) {
     const rawTags = tagInput.split(',').map((t) => t.trim().toLowerCase()).filter(Boolean);
     startTransition(async () => {
       try {
-        await updateProduct(formData);
-        await setProductTags(product.id, rawTags);
+        await updateProductWithTags(formData, rawTags);
         setSuccess(true);
         setIsOpen(false);
       } catch (err) {

frontend/app/admin/products/actions.ts

@@ -59,6 +59,59 @@ export async function setProductTags(productId: number, tags: string[]) {
   revalidatePath('/admin/products');
 }
 
+export async function updateProductWithTags(formData: FormData, tags: string[]) {
+  const id = Number(formData.get('id'));
+  const name = String(formData.get('name') || '').trim();
+  const canonicalName = String(formData.get('canonicalName') || '').trim();
+  const category = String(formData.get('category') || '').trim();
+  const subcategory = String(formData.get('subcategory') || '').trim();
+  const brand = String(formData.get('brand') || '').trim();
+  const categoryIdRaw = formData.get('categoryId');
+  const categoryId = categoryIdRaw !== '' && categoryIdRaw != null ? Number(categoryIdRaw) : null;
+
+  if (!name) throw new Error('Namn får inte vara tomt.');
+  if (name.length > 100) throw new Error('Namn får inte vara längre än 100 tecken.');
+  if (canonicalName.length > 100) throw new Error('Canonical name får inte vara längre än 100 tecken.');
+  if (category.length > 100) throw new Error('Kategori får inte vara längre än 100 tecken.');
+  if (subcategory.length > 100) throw new Error('Underkategori får inte vara längre än 100 tecken.');
+  if (brand.length > 100) throw new Error('Varumärke får inte vara längre än 100 tecken.');
+
+  const authHeaders = await getAuthHeaders();
+
+  const res = await fetch(`${API_BASE}/api/products/${id}`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json', ...authHeaders },
+    body: JSON.stringify({
+      name: name || undefined,
+      canonicalName: canonicalName || undefined,
+      category: category || null,
+      subcategory: subcategory || null,
+      brand: brand || null,
+      categoryId,
+    }),
+    cache: 'no-store',
+  });
+
+  if (!res.ok) {
+    const text = await res.text();
+    throw new Error(`Kunde inte uppdatera produkt: ${text}`);
+  }
+
+  const tagsRes = await fetch(`${API_BASE}/api/products/${id}/tags`, {
+    method: 'PUT',
+    headers: { 'Content-Type': 'application/json', ...authHeaders },
+    body: JSON.stringify({ tags }),
+    cache: 'no-store',
+  });
+
+  if (!tagsRes.ok) {
+    const text = await tagsRes.text();
+    throw new Error(`Kunde inte uppdatera taggar: ${text}`);
+  }
+
+  revalidatePath('/admin/products');
+}
+
 export async function deleteProduct(id: number) {
   const res = await fetch(`${API_BASE}/api/products/${id}`, {
     method: 'DELETE',