fix(recipes): address review feedback — shared type, design system tokens, test coverage

- Extract RecipeSummary type to $lib/recipes/types.ts (was duplicated in 3 files)
- Fix +page.svelte header link: replace Skeleton UI classes with design system tokens
- Fix h1: use font-[var(--font-display)] and correct size
- Fix FilterChipRow: text-[11px] → text-[13px] + tracking-[0.04em] per design system
- Fix RecipeCard metadata: text-[11px] → text-[12px] for readability
- Remove unused imports (vi, beforeEach, afterEach) from page.test.ts
- Add combined search + effort filter test
- Add reset-to-Alle filter test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/recipes/RecipeGrid.svelte

@@ -1,7 +1,6 @@
 <script lang="ts">
 	import RecipeCard from './RecipeCard.svelte';
-
-	type RecipeSummary = { id: string; name: string; cookTimeMin?: number; effort?: string; heroImageUrl?: string };
+	import type { RecipeSummary } from './types';
 
 	let { recipes }: { recipes: RecipeSummary[] } = $props();
 </script>