Fix billing data integrity, sale atomicity and stock safety

Bills were persisted correctly but read back wrong. The read path rebuilt a
cart from its lines alone, dropping bill-level discounts and loyalty, so every
figure derived from a stored bill was overstated: the upload payload, the day
archive and the shift report. A discounted 529 bill read back as 620.

Money and data integrity
- order_dao: restore bill_discount and points_redeemed when rebuilding a cart;
  keep the reconstruction tier-less so the membership discount is not applied
  twice. Trust the recorded total and points via SaleTransaction.storedTotal.
- checkout_sale + order_dao.commitSale: write the bill, its stock movement and
  the loyalty update in one transaction. Previously a failure part-way through
  left a persisted bill the cashier believed had failed, inviting a duplicate.
- checkout_sale: re-check every line against live stock. A parked bill resumed
  after its stock was sold passed validation and oversold.
- catalogue_dao: allocate the invoice sequence in one transaction; the previous
  read-modify-write could hand two sales the same number and fail UNIQUE.
- local_store: replay unsynced sales after a catalogue import, so a mid-shift
  re-import cannot restore stock that has already been sold.
- payment_controller: stamp the signed-in operator on the bill instead of the
  hardcoded seed session, and pass the terminal id through.
- cart: reconcile per-slab GST against the bill total so the parts sum to the
  whole on a tax invoice.

Sync and reporting
- sync_repository: drain unsynced bills in a loop rather than silently capping
  at one page; stop on rejection so rejected rows cannot loop forever.
- sync_log_dao (new): persist the sync history to the sync_log table, which the
  schema already defined but nothing used. It was in memory, so the only record
  that bills had been uploaded died at restart.
- Scope shift reports by cashier. day_archive is re-keyed to
  (business_date, cashier_name) so a till stays settleable after its bills are
  uploaded and deleted. Schema v4 with a migration that carries v3 rows across.

Input and UI
- barcode_service: consume machine-paced keystrokes so a scan cannot also land
  in the focused field, and raise the bar to 60ms/char while a text field has
  focus so typing a mobile number is not read as a scan. Clock and focus check
  injected so the behaviour is testable.
- primary_button: make the label flexible; label plus trailing total overflowed
  the Charge button by up to 131px.
- app_router: redirect instead of null-casting when the receipt route is
  entered without its transaction.
- customer_repository: reduce the search query to digits so a punctuated mobile
  number matches.

Cleanup
- Remove TransactionRepository.save, CustomerRepository.recordSale and
  OrderDao.insertOrder, all superseded by commitSale.
- dart fix across the tree; 251 analyzer issues down to 3 info-level.

Tests: 23 passing / 15 failing -> 90 passing. Fixed the two defects that broke
the existing suite (containsAll type argument, reset() needing a catalogue) and
deleted the leftover template test. Added coverage for the order round trip,
the day archive after a real sync, stock safety, checkout atomicity, the v3->v4
migration, scanner-versus-human input, and an app-level smoke test that renders
every module.

Note: bills already uploaded with a discount went up overstated. This stops it
happening again but does not correct historical server data.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

lib/domain/entities/transaction.dart

@@ -70,6 +70,8 @@ class SaleTransaction extends Equatable {
     required this.cashierName,
     this.status = TransactionStatus.completed,
     this.terminalId = 'TERM-01',
+    this.storedTotal,
+    this.storedPointsEarned,
   });
 
   final String id;
@@ -81,9 +83,20 @@ class SaleTransaction extends Equatable {
   final TransactionStatus status;
   final String terminalId;
 
+  /// The figure actually charged, as recorded at sale time.
+  ///
+  /// Set only when a bill is read back from storage. Deriving the total from
+  /// [cart] is correct for a live sale, but a rehydrated cart is a
+  /// reconstruction — if it ever loses a component the money must not move with
+  /// it. The recorded value wins whenever there is one.
+  final double? storedTotal;
+
+  /// Points issued by this sale, as recorded at sale time. See [storedTotal].
+  final int? storedPointsEarned;
+
   Customer? get customer => cart.customer;
 
-  double get total => cart.grandTotal;
+  double get total => storedTotal ?? cart.grandTotal;
 
   double get amountPaid =>
       payments.fold(0.0, (sum, p) => sum + p.amount).asMoney;
@@ -101,7 +114,7 @@ class SaleTransaction extends Equatable {
 
   bool get isSplit => payments.length > 1;
 
-  int get pointsEarned => cart.pointsEarned;
+  int get pointsEarned => storedPointsEarned ?? cart.pointsEarned;
   int get pointsRedeemed => cart.pointsRedeemed;
 
   String get paymentSummary =>