add bilingual labels to recipe components and fix language switcher

- Translate hardcoded German terms in IngredientsPage and InstructionsPage
- Migrate both components to Svelte 5 runes (, , )
- Fix language switcher to use correct short names via shared store
- Add recipeTranslationStore for recipe-specific language switching

src/lib/stores/recipeTranslation.ts

@@ -0,0 +1,9 @@
+import { writable } from 'svelte/store';
+
+interface RecipeTranslationData {
+	germanShortName: string;
+	englishShortName?: string;
+	hasEnglishTranslation: boolean;
+}
+
+export const recipeTranslationStore = writable<RecipeTranslationData | null>(null);