Use PointOfSaleObservableItemsController when GRDB is available

When grdbManager, catalogSyncCoordinator, and the pointOfSaleLocalCatalogi1
feature flag are all present, use the new PointOfSaleObservableItemsController
backed by GRDBObservableDataSource instead of the standard
PointOfSaleItemsController.

This enables reactive database-driven item lists for stores with local
catalog sync enabled.

Author: joshheald

Modules/Sources/PointOfSale/Presentation/PointOfSaleEntryPointView.swift

@@ -66,11 +66,23 @@ public struct PointOfSaleEntryPointView: View {
          services: POSDependencyProviding) {
         self.onPointOfSaleModeActiveStateChange = onPointOfSaleModeActiveStateChange
 
-        self.itemsController = PointOfSaleItemsController(
-            itemProvider: PointOfSaleItemService(currencySettings: services.currency.currencySettings),
-            itemFetchStrategyFactory: itemFetchStrategyFactory,
-            analyticsProvider: services.analytics
-        )
+        // Use observable controller with GRDB if available and feature flag is enabled, otherwise fall back to standard controller
+        // Note: We check feature flag here for eligibility. Once eligibility checking is
+        // refactored to be more centralized, this check can be simplified.
+        let isGRDBEnabled = services.featureFlags.isFeatureFlagEnabled(.pointOfSaleLocalCatalogi1)
+        if let grdbManager = grdbManager, catalogSyncCoordinator != nil, isGRDBEnabled {
+            self.itemsController = PointOfSaleObservableItemsController(
+                siteID: siteID,
+                grdbManager: grdbManager,
+                currencySettings: services.currency.currencySettings
+            )
+        } else {
+            self.itemsController = PointOfSaleItemsController(
+                itemProvider: PointOfSaleItemService(currencySettings: services.currency.currencySettings),
+                itemFetchStrategyFactory: itemFetchStrategyFactory,
+                analyticsProvider: services.analytics
+            )
+        }
         self.purchasableItemsSearchController = PointOfSaleItemsController(
             itemProvider: PointOfSaleItemService(currencySettings: services.currency.currencySettings),
             itemFetchStrategyFactory: itemFetchStrategyFactory,