Enhance workflow handling and enforce stricter exceptions

Enhanced `GetWorkflowsQueryHandler` to validate listing data
in workflow sources and return appropriate responses. Updated
`DocumentRepository.GetAsync` and `WorkflowRepository.CloseAsync`
to throw `NotSupportedException` for unimplemented functionality,
ensuring these methods cannot be used until finalized. Added
`DigitalData.TaskFlow.Domain.Enums` dependency to support new
logic in `GetWorkflowsQueryHandler`.

src/core/DigitalData.TaskFlow.Application/Features/Workflows/Queries/GetWorkflows/GetWorkflowsQuery.cs

@@ -1,6 +1,7 @@
 using DigitalData.TaskFlow.Application.Common.Factories;
 using DigitalData.TaskFlow.Application.Common.Interfaces;
 using DigitalData.TaskFlow.Domain.Common;
+using DigitalData.TaskFlow.Domain.Enums;
 using DigitalData.TaskFlow.Domain.Workflows;
 using FluentValidation;
 using MediatR;
@@ -44,6 +45,20 @@ public sealed class GetWorkflowsQueryHandler(IWorkflowRepository workflowReposit
     {
         var data = await workflowRepository.GetAsync(request.WisagId, cancellationToken);
 
+        var hasListingData = data.Sources
+            .SelectMany(source => source switch
+            {
+                FerdinandSourceBlock ferdinand => ferdinand.Listing,
+                ContractsSourceBlock contracts => contracts.Listing,
+                _ => []
+            })
+            .Any();
+
+        if (!hasListingData)
+        {
+            return ApiEnvelopeFactory.Create(data, MetaCode.NoOpenWorkflows);
+        }
+
         return ApiEnvelopeFactory.Create(data);
     }
 }

src/infrastructure/DigitalData.TaskFlow.Infrastructure/Repositories/DocumentRepository.cs

@@ -16,12 +16,7 @@ public sealed class DocumentRepository : IDocumentRepository
     /// <returns>Binary document payload.</returns>
     public Task<DocumentBinaryResult> GetAsync(string id, CancellationToken cancellationToken)
     {
-        return Task.FromResult(new DocumentBinaryResult
-        {
-            Content = [],
-            ContentType = "application/octet-stream",
-            FileName = $"{id}.bin",
-            Length = 0
-        });
+        throw new NotSupportedException(
+            "Document retrieval source (DB/DMS) is not finalized yet. Configure final integration before enabling GetAsync.");
     }
 }

src/infrastructure/DigitalData.TaskFlow.Infrastructure/Repositories/WorkflowRepository.cs

@@ -94,10 +94,7 @@ public sealed class WorkflowRepository(TaskFlowDbContext dbContext) : IWorkflowR
         CloseWorkflowDecision decision,
         CancellationToken cancellationToken)
     {
-        return Task.FromResult(new CloseWorkflowResult
-        {
-            ProcessId = processId,
-            IsClosed = true
-        });
+        throw new NotSupportedException(
+            "Closing write procedure is not finalized yet. Configure final DB procedure mapping before enabling CloseAsync.");
     }
 }