Implement progressive enhancement for universal search with context-aware filtering

Add comprehensive search solution that works across all recipe pages with proper fallbacks. Features include universal API endpoint, context-aware filtering (category/tag/icon/season/favorites), and progressive enhancement with form submission fallback for no-JS users.

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

src/routes/rezepte/favorites/+page.svelte

@@ -40,7 +40,7 @@ h1{
     {/if}
 </p>
 
-<Search></Search>
+<Search favoritesOnly={true}></Search>
 
 {#if data.error}
     <p class="empty-state">Fehler beim Laden der Favoriten: {data.error}</p>