Add cross-device grocery list sync via Nextcloud Cookbook API

Store a _groceryState JSON field on each recipe to track which
ingredients have been added, completed, or removed. Uses per-item
last-writer-wins conflict resolution with ISO 8601 timestamps.
Debounced push (2s) avoids excessive API calls; pull reconciles
on recipe open and app launch. Includes a settings toggle to
enable/disable sync.

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

Nextcloud Cookbook iOS Client/Data/ObservableRecipeDetail.swift

@@ -26,7 +26,8 @@ class ObservableRecipeDetail: ObservableObject {
     @Published var recipeIngredient: [String]
     @Published var recipeInstructions: [String]
     @Published var nutrition: [String:String]
-    
+    var groceryState: GroceryState?
+
     // Additional functionality
     @Published var ingredientMultiplier: Double
     
@@ -48,7 +49,8 @@ class ObservableRecipeDetail: ObservableObject {
         recipeIngredient = []
         recipeInstructions = []
         nutrition = [:]
-        
+        groceryState = nil
+
         ingredientMultiplier = 1
     }
     
@@ -68,7 +70,8 @@ class ObservableRecipeDetail: ObservableObject {
         recipeIngredient = recipeDetail.recipeIngredient
         recipeInstructions = recipeDetail.recipeInstructions
         nutrition = recipeDetail.nutrition
-        
+        groceryState = recipeDetail.groceryState
+
         ingredientMultiplier = Double(recipeDetail.recipeYield == 0 ? 1 : recipeDetail.recipeYield)
     }
     
@@ -90,7 +93,8 @@ class ObservableRecipeDetail: ObservableObject {
             tool: self.tool,
             recipeIngredient: self.recipeIngredient,
             recipeInstructions: self.recipeInstructions,
-            nutrition: self.nutrition
+            nutrition: self.nutrition,
+            groceryState: self.groceryState
         )
     }