refactor: move scaler out of $lib/server so it can run in browser

RecipeView needs scaleIngredients on the client for live portion scaling.
Moved scaler.ts from $lib/server/recipes/ to $lib/recipes/.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/components/RecipeView.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { scaleIngredients } from '$lib/server/recipes/scaler';
+  import { scaleIngredients } from '$lib/recipes/scaler';
   import type { Recipe } from '$lib/types';
 
   type Props = {

src/routes/recipes/[id]/print/+page.server.ts

@@ -0,0 +1,23 @@
+import type { PageServerLoad } from './$types';
+import { error } from '@sveltejs/kit';
+import { getDb } from '$lib/server/db';
+import { getRecipeById } from '$lib/server/recipes/repository';
+import { scaleIngredients } from '$lib/recipes/scaler';
+
+export const load: PageServerLoad = async ({ params, url }) => {
+  const id = Number(params.id);
+  if (!Number.isInteger(id) || id <= 0) error(400, { message: 'Invalid id' });
+  const recipe = getRecipeById(getDb(), id);
+  if (!recipe) error(404, { message: 'Nicht gefunden' });
+
+  const servingsParam = Number(url.searchParams.get('servings') ?? '');
+  const servings =
+    Number.isInteger(servingsParam) && servingsParam > 0
+      ? servingsParam
+      : (recipe.servings_default ?? 4);
+  const defaultServings = recipe.servings_default ?? 4;
+  const factor = servings / defaultServings;
+  const scaled = scaleIngredients(recipe.ingredients, factor);
+
+  return { recipe, ingredients: scaled, servings };
+};

tests/unit/scaler.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { scaleIngredients, roundQuantity } from '../../src/lib/server/recipes/scaler';
+import { scaleIngredients, roundQuantity } from '../../src/lib/recipes/scaler';
 import type { Ingredient } from '../../src/lib/types';
 
 const mk = (q: number | null, unit: string | null, name: string): Ingredient => ({