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/DTOs/Accounting/FinancialReportDtos.cs

@@ -6,6 +6,51 @@ namespace PowderCoating.Application.DTOs.Accounting;
 // without needing a separate round-trip to the company settings.
 
 
+// ── Cash Flow Statement ──────────────────────────────────────────────────────
+
+/// <summary>
+/// Cash Flow Statement using the direct (cash-basis) method for operating activities.
+/// Investing and Financing sections contain line items derived from account-level changes.
+/// BeginningCash + NetChangeInCash should equal EndingCash (within rounding tolerances).
+/// </summary>
+public class CashFlowStatementDto
+{
+    public string CompanyName { get; set; } = string.Empty;
+    public DateTime From { get; set; }
+    public DateTime To { get; set; }
+    public AccountingMethod Method { get; set; }
+
+    // ── Operating (direct / cash method) ───────────────────────────────────
+    /// <summary>Customer invoice payments received in the period.</summary>
+    public decimal CashFromCustomers { get; set; }
+    /// <summary>Vendor bill payments made in the period.</summary>
+    public decimal CashToVendors { get; set; }
+    /// <summary>Direct expense payments made in the period (not via bills).</summary>
+    public decimal CashForExpenses { get; set; }
+    public decimal NetOperating => CashFromCustomers - CashToVendors - CashForExpenses;
+
+    // ── Investing ──────────────────────────────────────────────────────────
+    public List<CashFlowLineDto> InvestingLines { get; set; } = new();
+    public decimal NetInvesting => InvestingLines.Sum(l => l.Amount);
+
+    // ── Financing ──────────────────────────────────────────────────────────
+    public List<CashFlowLineDto> FinancingLines { get; set; } = new();
+    public decimal NetFinancing => FinancingLines.Sum(l => l.Amount);
+
+    // ── Summary ────────────────────────────────────────────────────────────
+    public decimal BeginningCash { get; set; }
+    public decimal NetChangeInCash => NetOperating + NetInvesting + NetFinancing;
+    public decimal EndingCash => BeginningCash + NetChangeInCash;
+}
+
+/// <summary>A single line in the Investing or Financing section of the Cash Flow Statement.</summary>
+public class CashFlowLineDto
+{
+    public string Label { get; set; } = string.Empty;
+    /// <summary>Positive = cash inflow, negative = cash outflow.</summary>
+    public decimal Amount { get; set; }
+}
+
 // ── Customer / Vendor Statements ─────────────────────────────────────────────
 
 public class CustomerStatementDto