feat(api): add create and update product routes with authentication

refactor(admin): integrate router refresh after product updates in forms
fix(imports): update fetch paths for product creation and update in ReceiptImportClient

frontend/app/admin/products/AdminProductList.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useMemo, useEffect, useTransition } from 'react';
+import { useRouter } from 'next/navigation';
 import type { Product, Category } from '../../../features/inventory/types';
 import EditProductForm from './EditProductForm';
 import { bulkSetCategory, suggestBulkCategories } from './actions';
@@ -39,6 +40,7 @@ function flattenTree(nodes: CategoryNode[], depth = 0): { id: number; label: str
 }
 
 export default function AdminProductList({ products }: Props) {
+  const router = useRouter();
   const [search, setSearch] = useState('');
   const [sort, setSort] = useState('createdDesc');
   const [showUncategorizedOnly, setShowUncategorizedOnly] = useState(false);
@@ -127,6 +129,7 @@ export default function AdminProductList({ products }: Props) {
         await bulkSetCategory(ids, categoryId);
         setSelectedIds(new Set());
         setBulkCategoryId('');
+        router.refresh();
       } catch (err) {
         setBulkError(err instanceof Error ? err.message : 'Fel vid uppdatering');
       }

frontend/app/admin/products/EditProductForm.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useTransition, useEffect } from 'react';
+import { useRouter } from 'next/navigation';
 import type { Product } from '../../../features/inventory/types';
 import { updateProductWithTags, deleteProduct, suggestProductCategory } from './actions';
 
@@ -33,6 +34,7 @@ const inputStyle: React.CSSProperties = {
 };
 
 export default function EditProductForm({ product }: Props) {
+  const router = useRouter();
   const [isOpen, setIsOpen] = useState(false);
   const [isPending, startTransition] = useTransition();
   const [error, setError] = useState<string | null>(null);
@@ -107,6 +109,7 @@ export default function EditProductForm({ product }: Props) {
         await updateProductWithTags(formData, rawTags);
         setSuccess(true);
         setIsOpen(false);
+        router.refresh();
       } catch (err) {
         setError(err instanceof Error ? err.message : 'Okänt fel');
       }
@@ -120,6 +123,7 @@ export default function EditProductForm({ product }: Props) {
     startTransition(async () => {
       try {
         await deleteProduct(product.id);
+        router.refresh();
       } catch (err) {
         setError(err instanceof Error ? err.message : 'Okänt fel');
       }

frontend/app/admin/products/actions.ts

@@ -108,8 +108,6 @@ export async function updateProductWithTags(formData: FormData, tags: string[])
     const text = await tagsRes.text();
     throw new Error(`Kunde inte uppdatera taggar: ${text}`);
   }
-
-  revalidatePath('/admin/products');
 }
 
 export async function deleteProduct(id: number) {
@@ -123,8 +121,6 @@ export async function deleteProduct(id: number) {
     const text = await res.text();
     throw new Error(`Kunde inte ta bort produkt: ${text}`);
   }
-
-  revalidatePath('/admin/products');
 }
 
 export async function resetAllProducts() {
@@ -155,8 +151,6 @@ export async function bulkSetCategory(ids: number[], categoryId: number | null)
     const text = await res.text();
     throw new Error(`Kunde inte uppdatera produkter: ${text}`);
   }
-
-  revalidatePath('/admin/products');
 }
 
 export async function suggestProductCategory(productId: number) {