Redesign search tab, add category cards, recent recipes, and complete German translations

Overhaul SearchTabView with search history, empty/no-results states, and dynamic
navigation title. Extract CategoryCardView and RecentRecipesSection into standalone
views. Update RecipeTabView, RecipeListView, RecipeCardView, and MainView for the
modernized UI. Add all 12 missing German translations in Localizable.xcstrings.

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

Nextcloud Cookbook iOS Client/Views/MainView.swift

@@ -48,7 +48,15 @@ struct MainView: View {
             recipeViewModel.presentLoadingIndicator = true
             await appState.getCategories()
             await appState.updateAllRecipeDetails()
-            
+
+            // Preload category images
+            for category in appState.categories {
+                await appState.getCategoryImage(for: category.name)
+            }
+
+            // Load recently viewed recipes
+            await appState.loadRecentRecipes()
+
             // Open detail view for default category
             if UserSettings.shared.defaultCategory != "" {
                 if let cat = appState.categories.first(where: { c in