Add meal plan feature with cross-device sync and automatic stale data cleanup

Introduces weekly meal planning with a calendar-based tab view, per-recipe
date assignments synced via Nextcloud Cookbook custom metadata, and 30-day
automatic pruning of old entries on load, save, and sync merge.

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

Nextcloud Cookbook iOS Client/Data/UserSettings.swift

@@ -138,6 +138,12 @@ class UserSettings: ObservableObject {
             UserDefaults.standard.set(grocerySyncEnabled, forKey: "grocerySyncEnabled")
         }
     }
+
+    @Published var mealPlanSyncEnabled: Bool {
+        didSet {
+            UserDefaults.standard.set(mealPlanSyncEnabled, forKey: "mealPlanSyncEnabled")
+        }
+    }
     
     init() {
         self.username = UserDefaults.standard.object(forKey: "username") as? String ?? ""
@@ -161,6 +167,7 @@ class UserSettings: ObservableObject {
         self.groceryListMode = UserDefaults.standard.object(forKey: "groceryListMode") as? String ?? GroceryListMode.inApp.rawValue
         self.remindersListIdentifier = UserDefaults.standard.object(forKey: "remindersListIdentifier") as? String ?? ""
         self.grocerySyncEnabled = UserDefaults.standard.object(forKey: "grocerySyncEnabled") as? Bool ?? true
+        self.mealPlanSyncEnabled = UserDefaults.standard.object(forKey: "mealPlanSyncEnabled") as? Bool ?? true
         
         if authString == "" {
             if token != "" && username != "" {