Add WorkflowsClient for PDF validation and QR extraction

Introduced a new `WorkflowsClient` to orchestrate multi-step
operations, combining `IPdfValidationClient` and
`ISwissQrCodeClient`. Added methods to validate PDFs and extract
Swiss QR Codes in a single call, with overloads for byte arrays,
streams, and file paths. Registered `WorkflowsClient` as a scoped
service in `ServiceCollectionExtensions`.

Updated `PdfValidationResult` with an `IsValid` property to
simplify PDF validity checks. Added `IWorkflowsClient` interface
to define the contract for the new client, with detailed XML
documentation for its methods.

DocumentService.Client/Clients/WorkflowsClient.cs

@@ -0,0 +1,84 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Client.Interfaces;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Orchestrated multi-step workflows that compose multiple DocumentService clients
+/// into single, higher-level operations.
+/// </summary>
+public class WorkflowsClient(IPdfValidationClient validation, ISwissQrCodeClient swissQrCode) : IWorkflowsClient
+{
+    /// <inheritdoc />
+    public async Task<SwissQrCodeExtractionResult?> ExtractSwissQrCodeValidatedAsync(
+        byte[] pdfBytes,
+        bool raw = false,
+        bool throwIfInvalid = true,
+        CancellationToken cancellationToken = default)
+    {
+        var validationResult = await validation.ValidatePdfAsync(pdfBytes, cancellationToken);
+
+        if (!validationResult.IsValid)
+            return throwIfInvalid
+                ? throw new InvalidOperationException(
+                    $"PDF validation failed (IsEncrypted={validationResult.IsEncrypted}, " +
+                    $"PageCount={validationResult.PageCount}, FileSize={validationResult.FileSizeBytes}).")
+                : (SwissQrCodeExtractionResult?)null;
+
+        return await swissQrCode.ExtractSwissQrCodeAsync(pdfBytes, raw, cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<SwissQrCodeExtractionResult?> ExtractSwissQrCodeValidatedAsync(
+        Stream pdfStream,
+        bool raw = false,
+        bool throwIfInvalid = true,
+        CancellationToken cancellationToken = default)
+    {
+        var validationResult = await validation.ValidatePdfAsync(pdfStream, cancellationToken);
+
+        if (!validationResult.IsValid)
+            return throwIfInvalid
+                ? throw new InvalidOperationException(
+                    $"PDF validation failed (IsEncrypted={validationResult.IsEncrypted}, " +
+                    $"PageCount={validationResult.PageCount}, FileSize={validationResult.FileSizeBytes}).")
+                : (SwissQrCodeExtractionResult?)null;
+
+        // Stream was consumed by validation – reset if possible, otherwise re-open is caller's responsibility.
+        // Since callers typically pass a FileStream or MemoryStream, Position reset covers the common case.
+        if (pdfStream.CanSeek)
+            pdfStream.Position = 0;
+
+        return await swissQrCode.ExtractSwissQrCodeAsync(pdfStream, raw, cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<SwissQrCodeExtractionResult?> ExtractSwissQrCodeValidatedAsync(
+        string filePath,
+        bool raw = false,
+        bool throwIfInvalid = true,
+        CancellationToken cancellationToken = default)
+    {
+#if NETFRAMEWORK
+        using var stream = File.OpenRead(filePath);
+        var validationResult = await validation.ValidatePdfAsync(stream, cancellationToken);
+#else
+        var pdfBytes = await File.ReadAllBytesAsync(filePath, cancellationToken);
+        var validationResult = await validation.ValidatePdfAsync(pdfBytes, cancellationToken);
+#endif
+
+        if (!validationResult.IsValid)
+            return throwIfInvalid
+                ? throw new InvalidOperationException(
+                    $"PDF validation failed (IsEncrypted={validationResult.IsEncrypted}, " +
+                    $"PageCount={validationResult.PageCount}, FileSize={validationResult.FileSizeBytes}).")
+                : (SwissQrCodeExtractionResult?)null;
+
+#if NETFRAMEWORK
+        using var extractStream = File.OpenRead(filePath);
+        return await swissQrCode.ExtractSwissQrCodeAsync(extractStream, raw, cancellationToken);
+#else
+        return await swissQrCode.ExtractSwissQrCodeAsync(pdfBytes, raw, cancellationToken);
+#endif
+    }
+}