added product import and billing integration

lib/presentation/payment/providers/payment_controller.dart

@@ -4,7 +4,6 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../../app/providers.dart';
 import '../../../core/utils/extensions.dart';
-import '../../../data/sync/sync_engine.dart';
 import '../../../domain/entities/transaction.dart';
 import '../../../domain/usecases/checkout_sale.dart';
 import '../../auth/providers/auth_controller.dart';
@@ -80,29 +79,27 @@ class PaymentController extends StateNotifier<PaymentState> {
 
   /// Whether Complete Sale should be enabled.
   ///
-  /// Cash is the strict case: the drawer cannot be reconciled and no change can
-  /// be calculated unless the cashier states what was handed over. Card, UPI
-  /// and wallet settle on the external terminal, so they need no amount here.
+  /// Every method now requires the cashier to state what was actually
+  /// received before the sale can complete — a tap on Exact for the common
+  /// case, or a typed amount for a partial tender. `cashTendered` is the
+  /// amount entered for whichever method is currently active, not literally
+  /// cash; the name stayed to keep this change out of the rest of the app.
   bool get canConfirm {
     if (_billTotal <= 0) return false;
 
     // Staged splits already cover the bill.
     if (balanceDue <= 0.01) return true;
 
-    if (state.activeMethod.needsChange) {
-      return state.cashTendered >= balanceDue;
-    }
-    return true;
+    return state.cashTendered >= balanceDue;
   }
 
   /// Why the button is disabled, for display next to it.
   String? get blockedReason {
     if (_billTotal <= 0) return 'Add at least one item before charging.';
     if (canConfirm) return null;
-    if (state.activeMethod.needsChange) {
-      return 'Enter the cash received, or tap Exact.';
-    }
-    return null;
+    return state.activeMethod.needsChange
+        ? 'Enter the cash received, or tap Exact.'
+        : 'Enter the amount received, or tap Exact.';
   }
 
   void selectMethod(PaymentMethod method) {
@@ -212,10 +209,11 @@ class PaymentController extends StateNotifier<PaymentState> {
       _ref.invalidate(visibleProductsProvider);
       _ref.read(orderVersionProvider.notifier).state++;
 
-      // The bill is safely on disk; getting it to the back office is the
-      // engine's problem now. Deliberately not awaited — the cashier must
-      // reach the receipt screen at network speed of zero.
-      _ref.read(syncEngineProvider).nudge(SyncTrigger.saleCommitted);
+      // Deliberately NOT nudging the sync engine here. The bill sits on this
+      // terminal, unsynced, until the receipt screen's cancellation window
+      // closes — either it is pressed past early with New Sale, or the
+      // window runs out — or the sale is voided if the cashier cancels
+      // instead. See ReceiptScreen.
 
       return result;
     } on CheckoutFailure catch (e) {