feat: add untranslated recipes page for recipe admins

Add new page at /rezepte/untranslated for recipe admins to view and manage recipes without approved English translations. Includes translation status tracking, statistics dashboard, and visual badges.

Changes:
- Add API endpoint to fetch recipes without approved translations
- Create untranslated recipes page with auth checks for rezepte_users group
- Add translation status badges to Card component (pending, needs_update, none)
- Add database index on translations.en.translationStatus for performance
- Create layout for /rezepte route with header navigation
- Add "Unübersetzt" link to navigation for authorized users

src/models/Recipe.ts

@@ -100,5 +100,6 @@ const RecipeSchema = new mongoose.Schema(
 
 // Indexes for efficient querying
 RecipeSchema.index({ "translations.en.short_name": 1 });
+RecipeSchema.index({ "translations.en.translationStatus": 1 });
 
 export const Recipe = mongoose.model("Recipe", RecipeSchema);