added product import and billing integration

lib/data/datasources/local_store.dart

@@ -146,6 +146,18 @@ class LocalStore {
   String? get catalogueRevision => _catalogueRevision;
   int get unsyncedOrders => _unsyncedOrders;
 
+  /// Drops the imported catalogue from disk and from the in-memory cache.
+  ///
+  /// Called at sign-out so the next shift never bills against a copy left
+  /// over from this one — [hasCatalogue] goes back to false, and the only way
+  /// to sell again is a fresh pull from the back office.
+  Future<void> clearCatalogue() async {
+    await catalogue.clearCatalogue();
+    _products.clear();
+    _lastImportAt = null;
+    _catalogueRevision = null;
+  }
+
   Future<void> importCatalogue({
     required List<Product> products,
     required List<Customer> customers,