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/presentation/auth/screens/login_screen.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_animate/flutter_animate.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
@@ -408,14 +407,14 @@ class _FormPanel extends ConsumerWidget {
                     const SizedBox(height: AppSpacing.sm),
                     Container(
                       padding: const EdgeInsets.all(AppSpacing.md),
-                      decoration: BoxDecoration(
+                      decoration: const BoxDecoration(
                         color: AppColors.dangerSurface,
                         borderRadius: AppRadius.brSm,
                       ),
                       child: Row(
                         children: [
                           const Icon(Icons.error_outline_rounded,
-                              color: AppColors.danger, size: 18),
+                              color: AppColors.danger, size: 18,),
                           const SizedBox(width: AppSpacing.sm),
                           Expanded(
                             child: Text(
@@ -509,13 +508,13 @@ class _DemoHint extends StatelessWidget {
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
           const Icon(Icons.info_outline_rounded,
-              size: 17, color: AppColors.primary),
+              size: 17, color: AppColors.primary,),
           const SizedBox(width: AppSpacing.sm),
-          Expanded(
+          const Expanded(
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: [
-                const Text(
+                Text(
                   'Demo account',
                   style: TextStyle(
                     fontSize: 12.5,
@@ -523,10 +522,10 @@ class _DemoHint extends StatelessWidget {
                     color: AppColors.primary,
                   ),
                 ),
-                const SizedBox(height: 2),
+                SizedBox(height: 2),
                 SelectableText(
                   '${DemoCredentials.email} · ${DemoCredentials.password}',
-                  style: const TextStyle(
+                  style: TextStyle(
                     fontSize: 12,
                     color: AppColors.textSecondary,
                   ),