feat(shopping): setCartServings mit Positiv-Validation

src/lib/server/shopping/repository.ts

@@ -55,11 +55,16 @@ export function removeRecipeFromCart(
 }
 
 export function setCartServings(
-  _db: Database.Database,
-  _recipeId: number,
-  _servings: number
+  db: Database.Database,
+  recipeId: number,
+  servings: number
 ): void {
-  throw new Error('not implemented');
+  if (!Number.isInteger(servings) || servings <= 0) {
+    throw new Error(`Invalid servings: ${servings}`);
+  }
+  db.prepare(
+    'UPDATE shopping_cart_recipe SET servings = ? WHERE recipe_id = ?'
+  ).run(servings, recipeId);
 }
 
 export function listShoppingList(db: Database.Database): ShoppingListSnapshot {

tests/integration/shopping-repository.test.ts

@@ -4,7 +4,8 @@ import { insertRecipe } from '../../src/lib/server/recipes/repository';
 import {
   addRecipeToCart,
   removeRecipeFromCart,
-  listShoppingList
+  listShoppingList,
+  setCartServings
 } from '../../src/lib/server/shopping/repository';
 import type { Recipe } from '../../src/lib/types';
 
@@ -84,3 +85,21 @@ describe('removeRecipeFromCart', () => {
     expect(() => removeRecipeFromCart(db, id)).not.toThrow();
   });
 });
+
+describe('setCartServings', () => {
+  it('updates servings for a cart recipe', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe());
+    addRecipeToCart(db, id, null, 4);
+    setCartServings(db, id, 8);
+    expect(listShoppingList(db).recipes[0].servings).toBe(8);
+  });
+
+  it('rejects non-positive servings', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe());
+    addRecipeToCart(db, id, null, 4);
+    expect(() => setCartServings(db, id, 0)).toThrow();
+    expect(() => setCartServings(db, id, -3)).toThrow();
+  });
+});