Phase F: Customer/Vendor Statements, Payment Terms Parser, Tax Rates

F1: GetCustomerStatementAsync/GetVendorStatementAsync on IFinancialReportService;
    StatementLineDto; CustomerStatementDto/VendorStatementDto; Statement action on
    CustomersController + VendorsController; Statement views + PDF download via
    StatementPdfHelper (QuestPDF); Statement button on Customer/Vendor Details pages.

F2: PaymentTermsParser static helper (CalculateDueDate, ParseEarlyPaymentDiscount);
    EarlyPaymentDiscountPercent/Days on Invoice entity; GetCustomerPaymentTerms AJAX
    endpoint on InvoicesController auto-populates Terms + due date on customer select;
    early payment discount notice on Invoice Create.

F3: TaxRate entity (Name/Rate/State/IsDefault/IsActive, tenant-filtered);
    IUnitOfWork.TaxRates + UnitOfWork + ApplicationDbContext; TaxRatesController
    (Index/Create/Edit/Delete/ToggleActive, CompanyAdminOnly); GetTaxRateForCustomer
    AJAX endpoint; Tax Rates in Settings gear menu.

Also fixes AddVendorCredits migration: VendorCreditApplications FKs changed from
CASCADE to NoAction to resolve SQL Server error 1785 (multiple cascade paths).
Migration: AddPaymentTermsAndTaxRates applied locally; 200/200 unit tests pass.

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

src/PowderCoating.Application/DTOs/Accounting/FinancialReportDtos.cs

@@ -6,6 +6,47 @@ namespace PowderCoating.Application.DTOs.Accounting;
 // without needing a separate round-trip to the company settings.
 
 
+// ── Customer / Vendor Statements ─────────────────────────────────────────────
+
+public class CustomerStatementDto
+{
+    public int CustomerId { get; set; }
+    public string CustomerName { get; set; } = string.Empty;
+    public string CompanyName { get; set; } = string.Empty;
+    public string? CustomerAddress { get; set; }
+    public DateTime From { get; set; }
+    public DateTime To { get; set; }
+    public decimal OpeningBalance { get; set; }
+    public List<StatementLineDto> Lines { get; set; } = new();
+    public decimal ClosingBalance { get; set; }
+}
+
+public class VendorStatementDto
+{
+    public int VendorId { get; set; }
+    public string VendorName { get; set; } = string.Empty;
+    public string CompanyName { get; set; } = string.Empty;
+    public DateTime From { get; set; }
+    public DateTime To { get; set; }
+    public decimal OpeningBalance { get; set; }
+    public List<StatementLineDto> Lines { get; set; } = new();
+    public decimal ClosingBalance { get; set; }
+}
+
+public class StatementLineDto
+{
+    public DateTime Date { get; set; }
+    /// <summary>E.g., "Invoice", "Payment", "Credit Applied", "Deposit Applied".</summary>
+    public string Type { get; set; } = string.Empty;
+    public string Reference { get; set; } = string.Empty;
+    public string Description { get; set; } = string.Empty;
+    /// <summary>Amount added to the balance (invoice for customer, bill for vendor).</summary>
+    public decimal? Debit { get; set; }
+    /// <summary>Amount reducing the balance (payment, credit).</summary>
+    public decimal? Credit { get; set; }
+    public decimal RunningBalance { get; set; }
+}
+
 // ── AP Aging ──────────────────────────────────────────────────────────────────
 
 public class ApAgingReportDto

src/PowderCoating.Application/Interfaces/IFinancialReportService.cs

@@ -35,4 +35,10 @@ public interface IFinancialReportService
 
     /// <summary>Looks up the accounting method configured for the given company. Returns Accrual if not found.</summary>
     Task<AccountingMethod> GetCompanyAccountingMethodAsync(int companyId);
+
+    /// <summary>Returns a dated activity statement for a customer showing opening balance, all transactions in the period, and closing balance.</summary>
+    Task<CustomerStatementDto> GetCustomerStatementAsync(int companyId, int customerId, DateTime from, DateTime to);
+
+    /// <summary>Returns a dated activity statement for a vendor showing opening balance, all transactions in the period, and closing balance.</summary>
+    Task<VendorStatementDto> GetVendorStatementAsync(int companyId, int vendorId, DateTime from, DateTime to);
 }