Fix category handling, recipe management, and dark mode toggle tint

- Map uncategorized category between * (internal) and empty string
  (API) so selecting Sonstige/Other correctly persists to the server
- Default new recipes to Other (*) category and remove None option
- Add "New Category" option to category picker in recipe edit view
- Include newly created/imported recipes in recently viewed list and
  pre-fetch thumbnails so images display immediately
- Remove deleted recipes from recently viewed list
- Remove broad .tint(.primary) from RecipeTabView that caused white
  toggles in Settings during dark mode
- Rename German "Other" translation from Andere to Sonstige
- Add missing translations for Servings stepper and new category strings

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Nextcloud Cookbook iOS Client/Views/Tabs/RecipeTabView.swift

@@ -163,7 +163,6 @@ struct RecipeTabView: View {
                 }
             }
         }
-        .tint(.primary)
         .sheet(isPresented: $viewModel.showImportURLSheet) {
             ImportURLSheet { recipeDetail in
                 viewModel.navigateToImportedRecipe(recipeDetail: recipeDetail)