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/SettingsView.swift

@@ -26,7 +26,7 @@ struct SettingsView: View {
                 Picker("Select a default cookbook", selection: $userSettings.defaultCategory) {
                     Text("None").tag("None")
                     ForEach(appState.categories, id: \.name) { category in
-                        Text(category.name == "*" ? "Other" : category.name).tag(category)
+                        Text(category.name == "*" ? String(localized: "Other") : category.name).tag(category)
                     }
                 }
             } header: {