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/server/recipes/scaler.ts

@@ -1,16 +0,0 @@
-import type { Ingredient } from '$lib/types';
-
-export function roundQuantity(q: number): number {
-  if (q === 0) return 0;
-  if (q < 1) return Math.round(q * 100) / 100;
-  if (q < 10) return Math.round(q * 10) / 10;
-  return Math.round(q);
-}
-
-export function scaleIngredients(ings: Ingredient[], factor: number): Ingredient[] {
-  if (factor <= 0) throw new Error('factor must be positive');
-  return ings.map((i) => ({
-    ...i,
-    quantity: i.quantity === null ? null : roundQuantity(i.quantity * factor)
-  }));
-}