fix: use dynamic recipeLang in API calls instead of hardcoded /api/rezepte

Client-side navigation to /recipes hung because getUserFavorites and
other endpoints were hardcoded to /api/rezepte, causing fetch mismatches
during SvelteKit's client-side routing.

src/lib/components/FavoriteButton.svelte

@@ -1,9 +1,12 @@
 <script lang="ts">
   import { browser } from '$app/environment';
   import { enhance } from '$app/forms';
+  import { page } from '$app/stores';
 
   let { recipeId, isFavorite = $bindable(false), isLoggedIn = false } = $props<{ recipeId: string, isFavorite?: boolean, isLoggedIn?: boolean }>();
 
+  const recipeLang = $derived($page.url.pathname.split('/')[1] || 'rezepte');
+
   let isLoading = $state(false);
 
   async function toggleFavorite(event: Event) {
@@ -17,7 +20,7 @@
       
       try {
         const method = isFavorite ? 'DELETE' : 'POST';
-        const response = await fetch('/api/rezepte/favorites', {
+        const response = await fetch(`/api/${recipeLang}/favorites`, {
           method,
           headers: {
             'Content-Type': 'application/json',

src/lib/components/recipes/Search.svelte

@@ -284,7 +284,7 @@
                 const apiBase = `/api/${isEnglish ? 'recipes' : 'rezepte'}`;
                 const [tagsRes, iconsRes] = await Promise.all([
                     fetch(`${apiBase}/items/tag`),
-                    fetch('/api/rezepte/items/icon')
+                    fetch(`${apiBase}/items/icon`)
                 ]);
                 availableTags = await tagsRes.json();
                 availableIcons = await iconsRes.json();