Phase H: Add Cash Flow Statement (direct / cash-basis method)

- CashFlowStatementDto (Operating, Investing, Financing sections; BeginningCash/EndingCash)
- CashFlowLineDto for Investing/Financing line items
- GetCashFlowStatementAsync on IFinancialReportService + implementation in FinancialReportService
- GenerateCashFlowStatementPdfAsync on IPdfService + QuestPDF implementation in PdfService
- ReportsController.CashFlowStatement GET + CashFlowStatementPdf GET with inline/download mode
- CashFlowStatement.cshtml view with date filter, 3-section cards, summary sidebar, methodology note
- Reports Landing page: Cash Flow Statement card added to Accounting section

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

src/PowderCoating.Application/Interfaces/IFinancialReportService.cs

@@ -41,4 +41,12 @@ public interface IFinancialReportService
 
     /// <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);
+
+    /// <summary>
+    /// Returns a Cash Flow Statement for the period using the direct (cash-basis) method for
+    /// operating activities. Investing and Financing sections are derived from account-level data.
+    /// BeginningCash is computed from all cash/bank account credits and debits prior to
+    /// <paramref name="from"/>; EndingCash adds the net change during the period.
+    /// </summary>
+    Task<CashFlowStatementDto> GetCashFlowStatementAsync(int companyId, DateTime from, DateTime to);
 }