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/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) {