Fix meal plan not populating on first login and add pull-to-refresh sync

Rewrite MealPlanSyncManager.performSync() (renamed from performInitialSync) to
discover _mealPlanAssignment metadata from all server recipes, not just locally-
known ones. On first sync all recipes are checked; on subsequent syncs only
recipes modified since lastMealPlanSyncDate are fetched (max 5 concurrent).

Trigger meal plan sync from pull-to-refresh on both the recipe and meal plan
tabs, and from the "Refresh all" toolbar button.

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

Nextcloud Cookbook iOS Client/Data/GroceryStateSyncManager.swift

@@ -101,7 +101,7 @@ class GroceryStateSyncManager {
     // MARK: - Initial Sync
 
     /// Pushes any local-only items and reconciles server items on app launch.
-    func performInitialSync() async {
+    func performSync() async {
         guard let appState, let groceryManager else { return }
 
         await loadPendingRemovals()
@@ -208,7 +208,7 @@ class GroceryStateSyncManager {
     // MARK: - Pending Removal Tracking
 
     /// Records a recipe ID whose grocery items were fully removed, so that
-    /// `performInitialSync` can push the deletion even after the key disappears
+    /// `performSync` can push the deletion even after the key disappears
     /// from `groceryDict`.
     func trackPendingRemoval(recipeId: String) {
         pendingRemovalRecipeIds.insert(recipeId)