feat(meal-plan): add servings field to MealPlanEntry and update related functionality

feat(products): implement bulk update for product categories

feat(recipes): add servings input to WriteRecipePage and update MealPlanClient for servings management

refactor(types): enhance Product and Category types with additional properties

frontend/app/admin/products/actions.ts

@@ -88,3 +88,20 @@ export async function resetAllProducts() {
 
   revalidatePath('/admin/products');
 }
+
+export async function bulkSetCategory(ids: number[], categoryId: number | null) {
+  if (ids.length === 0) return;
+  const res = await fetch(`${API_BASE}/api/products/bulk-update`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', ...(await getAuthHeaders()) },
+    body: JSON.stringify({ ids, categoryId }),
+    cache: 'no-store',
+  });
+
+  if (!res.ok) {
+    const text = await res.text();
+    throw new Error(`Kunde inte uppdatera produkter: ${text}`);
+  }
+
+  revalidatePath('/admin/products');
+}