[CLAUDE] App: Plan B Chunk E1 — CreateContractCommand +ApprovalWorkflowId V2 pin field

Mirror PE CreatePurchaseEvaluationCommand pattern. Drafter pick V2 workflow
qua Workspace Select dropdown (Chunk D FE Implementer running parallel) →
ApprovalWorkflowId pin lúc create. Fallback V1 auto activeWfId nếu null
(7 prod contract giữ behavior).

Changes:
- CreateContractCommand record +Guid? ApprovalWorkflowId = null (optional)
- Handler line 96 wire entity.ApprovalWorkflowId = request.ApprovalWorkflowId
- Both V1 + V2 fields persist (Service ApproveV2Async branch dispatch theo V2 first)

Verify:
- dotnet build PASS 0 err
- Backward compat: existing caller (KHÔNG pass ApprovalWorkflowId) → fallback null
- V1 contract path UNCHANGED

Plan B chain status:
- A1 58898e8 ✅ Entity
- A2 a85e437 ✅ Mig 32 + Seed
- B 138469d ✅ Service ApproveV2 branch
- C 26c98d3 ✅ Mig 33 LevelOpinions
- B2 1f199b0 ✅ UPSERT block
- E1 (this) ✅ CreateContractCommand +ApprovalWorkflowId
- D FE Workspace V2 (Implementer running parallel)
- E2 ContractDetailDto + GetContractByIdQuery extend (em main pending)
- E3 FE Section 5 LevelOpinionsV2 (Implementer pending sau E2)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Backend/SolutionErp.Application/Contracts/ContractFeatures.cs

@@ -27,7 +27,13 @@ public record CreateContractCommand(
     string? DraftData,
     Guid? BudgetId,
     string? BudgetManualName,
-    decimal? BudgetManualAmount) : IRequest<Guid>;
+    decimal? BudgetManualAmount,
+    // [Plan B S29 2026-05-22 Chunk E1] Drafter pick V2 workflow lúc create —
+    // mirror PE pattern Workspace Select dropdown. Nếu null → fallback V1 auto
+    // pick activeWfId (7 prod contract giữ behavior). Mutually exclusive với
+    // V1: pin V2 + V1 cùng lúc OK schema (cả 2 nullable) — Service ApproveV2Async
+    // branch ưu tiên V2 nếu cả 2 set.
+    Guid? ApprovalWorkflowId = null) : IRequest<Guid>;
 
 public class CreateContractCommandValidator : AbstractValidator<CreateContractCommand>
 {
@@ -94,6 +100,10 @@ public class CreateContractCommandHandler(
             BudgetManualName = request.BudgetManualName,
             BudgetManualAmount = request.BudgetManualAmount,
             WorkflowDefinitionId = activeWfId,
+            // [Plan B S29 2026-05-22 Chunk E1] Pin V2 workflow nếu Drafter pick
+            // qua Workspace Select dropdown (Chunk D FE). Cả 2 set ok — Service
+            // ApproveV2Async branch dispatch theo ApprovalWorkflowId trước.
+            ApprovalWorkflowId = request.ApprovalWorkflowId,
             SlaDeadline = DateTime.UtcNow.Add(workflow.GetPhaseSla(ContractPhase.DangSoanThao) ?? TimeSpan.FromDays(7)),
         };