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.Web/Controllers/CustomersController.cs

@@ -26,6 +26,7 @@ public class CustomersController : Controller
     private readonly ISubscriptionService _subscriptionService;
     private readonly ITenantContext _tenantContext;
     private readonly UserManager<ApplicationUser> _userManager;
+    private readonly IFinancialReportService _financialReports;
 
     public CustomersController(
         IUnitOfWork unitOfWork,
@@ -34,7 +35,8 @@ public class CustomersController : Controller
         INotificationService notificationService,
         ISubscriptionService subscriptionService,
         ITenantContext tenantContext,
-        UserManager<ApplicationUser> userManager)
+        UserManager<ApplicationUser> userManager,
+        IFinancialReportService financialReports)
     {
         _unitOfWork = unitOfWork;
         _mapper = mapper;
@@ -43,6 +45,7 @@ public class CustomersController : Controller
         _subscriptionService = subscriptionService;
         _tenantContext = tenantContext;
         _userManager = userManager;
+        _financialReports = financialReports;
     }
 
     /// <summary>
@@ -935,6 +938,30 @@ public class CustomersController : Controller
         return RedirectToAction(nameof(Details), new { id });
     }
 
+    /// <summary>
+    /// Displays or downloads a dated activity statement for a customer.
+    /// Pass <c>pdf=true</c> to download the QuestPDF version; otherwise renders the HTML view.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> Statement(int id, DateTime? from, DateTime? to, bool pdf = false)
+    {
+        var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;
+        var fromDate  = from ?? new DateTime(DateTime.Today.Year, DateTime.Today.Month, 1);
+        var toDate    = to   ?? DateTime.Today;
+
+        var dto = await _financialReports.GetCustomerStatementAsync(companyId, id, fromDate, toDate);
+
+        if (pdf)
+        {
+            var bytes = StatementPdfHelper.Generate(
+                dto.CustomerName, dto.CompanyName, dto.CustomerAddress,
+                dto.From, dto.To, dto.OpeningBalance, dto.Lines, dto.ClosingBalance, isVendor: false);
+            return File(bytes, "application/pdf", $"Statement-{dto.CustomerName}-{toDate:yyyyMMdd}.pdf");
+        }
+
+        return View(dto);
+    }
+
     /// <summary>
     /// Generates the next sequential credit memo number in CM-YYMM-#### format.
     /// Uses <c>ignoreQueryFilters: true</c> when scanning all existing memos so that