Add Apple Reminders integration for grocery list with local mapping persistence

Introduce a GroceryListManager facade that delegates to either the existing
in-app GroceryList or a new RemindersGroceryStore backed by EventKit. Users
choose the mode in Settings; when Reminders mode is active the Grocery List
tab is hidden. Recipe-to-reminder grouping uses a local mapping file
(reminder_mappings.data) instead of polluting the reminder's notes field,
with automatic pruning when reminders are deleted externally.

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

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

@@ -11,7 +11,7 @@ import SwiftUI
 
 
 struct GroceryListTabView: View {
-    @EnvironmentObject var groceryList: GroceryList
+    @EnvironmentObject var groceryList: GroceryListManager
 
     var body: some View {
         NavigationStack {

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

@@ -12,7 +12,7 @@ import SwiftUI
 
 struct RecipeTabView: View {
     @EnvironmentObject var appState: AppState
-    @EnvironmentObject var groceryList: GroceryList
+    @EnvironmentObject var groceryList: GroceryListManager
     @EnvironmentObject var viewModel: RecipeTabView.ViewModel
     @Environment(\.horizontalSizeClass) private var horizontalSizeClass
 
@@ -110,6 +110,7 @@ struct RecipeTabView: View {
                     case .settings:
                         SettingsView()
                             .environmentObject(appState)
+                            .environmentObject(groceryList)
                     case .newRecipe:
                         RecipeView(viewModel: RecipeView.ViewModel())
                             .environmentObject(appState)