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>

src/PowderCoating.Core/Entities/Refund.cs

@@ -22,6 +22,10 @@ public class Refund : BaseEntity
     public DateTime? IssuedDate { get; set; }
     public string? IssuedById { get; set; }
 
+    /// <summary>Bank/checking account the refund was paid from. Mirrors Payment.DepositAccountId so
+    /// the Trial Balance can credit this account when computing bank balance.</summary>
+    public int? DepositAccountId { get; set; }
+
     // For store-credit refunds: the CreditMemo created on their behalf
     public int? CreditMemoId { get; set; }