Close all GL entry gaps across the accounting surface

- Stripe payments/refunds/chargebacks now post DR/CR entries (PaymentController)
- Vendor credit void now reverses the posted GL lines (VendorCreditsController)
- Gift certificate issue/redeem/void post GL to account 2500 GC Liability;
  FinancialReportService Trial Balance + Balance Sheet include GC liability and
  breakage income; P&L shows deferred revenue deduction and breakage income line
- Customer deposits now post DR Checking / CR 2300 on record, reverse on delete;
  invoice auto-apply uses DR 2300 / CR AR (not a second bank debit); draft
  invoice delete reverses deposit-apply GL before the AR reversal
- Deposit.DepositAccountId column added; account 2300 seeded via migration
- InvoicesController.ApplyCredit now posts DR Sales Discounts / CR AR,
  consistent with CreditMemosController.Apply
- IssueRefund (cash/card) posts DR AR / CR Bank and sets Refund.DepositAccountId;
  refund modal gains a bank account selector hidden for store-credit path
- CancelRefund (cash/card) reverses the IssueRefund GL entries
- LedgerService GetAccountLedgerAsync + ComputePriorBalanceAsync now include
  Refunds, CreditMemoApplications, VendorCreditApplications, GC Liability (2500),
  and Customer Deposits (2300) so account ledger view and RecalculateAllAsync
  produce correct balances
- Three EF migrations applied: SeedSalesDiscountsAccount, AccountingGapsPhase2,
  AccountingDepositsGL
- Unit tests updated for new IAccountBalanceService constructor params (200/200)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/PowderCoating.UnitTests/DepositsControllerTests.cs

@@ -292,7 +292,8 @@ public class DepositsControllerTests
             uow,
             userManager.Object,
             Mock.Of<ILogger<DepositsController>>(),
-            Mock.Of<ICompanyLogoService>());
+            Mock.Of<ICompanyLogoService>(),
+            Mock.Of<IAccountBalanceService>());
 
         controller.ControllerContext = new ControllerContext
         {