refactor(shopping): DEFAULT_SERVINGS-Konstante + Kommentare

src/lib/server/shopping/repository.ts

@@ -1,5 +1,9 @@
 import type Database from 'better-sqlite3';
 
+// Fallback when a recipe has no servings_default set — matches the default
+// used by RecipeEditor's "new recipe" template.
+const DEFAULT_SERVINGS = 4;
+
 export type ShoppingCartRecipe = {
   recipe_id: number;
   title: string;
@@ -33,7 +37,9 @@ export function addRecipeToCart(
   const row = db
     .prepare('SELECT servings_default FROM recipe WHERE id = ?')
     .get(recipeId) as { servings_default: number | null } | undefined;
-  const resolved = servings ?? row?.servings_default ?? 4;
+  const resolved = servings ?? row?.servings_default ?? DEFAULT_SERVINGS;
+  // ON CONFLICT updates only servings — added_by_profile_id stays with the
+  // first profile that added the recipe (household cart, audit trail).
   db.prepare(
     `INSERT INTO shopping_cart_recipe (recipe_id, servings, added_by_profile_id)
      VALUES (?, ?, ?)
@@ -63,6 +69,8 @@ export function listShoppingList(db: Database.Database): ShoppingListSnapshot {
         ORDER BY cr.added_at ASC`
     )
     .all() as ShoppingCartRecipe[];
+  // TODO(Task 6): rows + uncheckedCount are populated by the aggregation query.
+  // Until then, callers must not rely on these fields.
   return { recipes, rows: [], uncheckedCount: 0 };
 }