[CLAUDE] Domain+Infra: Migration 18 PE workflow inner steps + User.PositionLevel (Chunk A)

N-stage workflow approval — mỗi WorkflowStep cha (= 1 phase) cấu hình
được chuỗi InnerSteps con theo Department × PositionLevel với Order
sequential. Phase 9+ feature, mở rộng từ 2-stage Mig 16.

Schema:
- enum PositionLevel { NhanVien=1, PhoPhong=2, TruongPhong=3 } (Domain/Identity)
- ALTER Users + PositionLevel int? NULL (admin/system user vẫn null)
- CREATE TABLE PurchaseEvaluationWorkflowStepInnerSteps:
  Id PK, PurchaseEvaluationWorkflowStepId FK Cascade,
  Order int, DepartmentId FK Restrict, PositionLevel int,
  Name nvarchar(200), SlaDays int?, IsRequired bit
- ALTER PurchaseEvaluationDepartmentApprovals + InnerStepId Guid? FK Restrict
  (null cho data legacy 2-stage Review/Confirm Mig 16)

Backward compat: step KHÔNG có InnerSteps → service fallback logic
2-stage Stage=Review|Confirm cũ (Chunk C). Data Mig 16 hiện có giữ
nguyên, InnerStepId=null.

Verify:
- dotnet build SolutionErp.slnx pass (0 error, 2 pre-existing warning DocxRenderer)
- dotnet ef database update LocalDB applied OK
- dotnet test SolutionErp.slnx 83 pass (54 Domain + 29 Infra) — no regression
- 3-file rule: Migration.cs + Designer.cs + Snapshot updated

Pending Chunk B: Application CQRS — extend CreatePeWorkflowDefinitionCommand
với InnerSteps DTO + UpdateUserPositionLevelCommand.

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

src/Backend/SolutionErp.Domain/Identity/PositionLevel.cs

@@ -0,0 +1,16 @@
+namespace SolutionErp.Domain.Identity;
+
+// Cấp chức danh trong phòng ban — phục vụ N-stage workflow inner step (Mig 18).
+// Mỗi WorkflowStep cha (= 1 phase) có thể cấu hình 1 chuỗi inner step
+// con (Order asc) khớp Department × PositionLevel. Ai đúng phòng + đúng cấp
+// (+ Order tiếp theo chưa duyệt) thì duyệt được.
+//
+// Default null cho admin/system/external user không thuộc cấp cụ thể.
+// CanBypassReview=true ở User cho phép cấp cao hơn (TP) skip cấp dưới
+// (NV+PP) cùng Department khi duyệt 1 inner step block.
+public enum PositionLevel
+{
+    NhanVien = 1,        // NV
+    PhoPhong = 2,        // PP
+    TruongPhong = 3,     // TP
+}

src/Backend/SolutionErp.Domain/Identity/User.cs

@@ -18,6 +18,13 @@ public class User : IdentityUser<Guid>
 
     // 2-stage department approval (Phase 9 — Migration 16): khi true, NV
     // được quyền duyệt thay TPB (skip Stage Review, đẩy thẳng Stage Confirm).
+    // Cũng dùng cho N-stage inner step (Mig 18) — TP có CanBypassReview
+    // skip NV+PP cùng Department.
     // Mặc định false (an toàn). Admin set ở UserManager UI.
     public bool CanBypassReview { get; set; }
+
+    // Cấp chức danh trong phòng — phục vụ N-stage workflow inner step (Mig 18).
+    // Mỗi inner step yêu cầu user khớp DepartmentId + PositionLevel mới duyệt
+    // được sub-step đó. Null cho admin/system/external user.
+    public PositionLevel? PositionLevel { get; set; }
 }

src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationDepartmentApproval.cs

@@ -15,12 +15,18 @@ public class PurchaseEvaluationDepartmentApproval : AuditableEntity
     public Guid PurchaseEvaluationId { get; set; }
     public int PhaseAtApproval { get; set; }              // snapshot PurchaseEvaluationPhase int
     public Guid DepartmentId { get; set; }
-    public ApprovalStage Stage { get; set; }               // 1=Review (NV), 2=Confirm (TPB)
+    public ApprovalStage Stage { get; set; }               // 1=Review (NV), 2=Confirm (TPB) — legacy 2-stage Mig 16
     public Guid ApproverUserId { get; set; }
     public string? ApproverRoleSnapshot { get; set; }
     public string? Comment { get; set; }
     public DateTime ApprovedAt { get; set; }
     public bool IsBypassed { get; set; }
 
+    // N-stage inner step link (Mig 18) — null cho data legacy 2-stage Review/Confirm.
+    // Có giá trị khi step cha có InnerSteps configured → mỗi sub-step approve =
+    // 1 row riêng với InnerStepId set. Cùng Stage=Confirm (legacy field giữ nguyên
+    // cho backward compat — N-stage không dùng Review/Confirm semantics).
+    public Guid? InnerStepId { get; set; }
+
     public PurchaseEvaluation? PurchaseEvaluation { get; set; }
 }

src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationWorkflowDefinition.cs

@@ -1,5 +1,6 @@
 using SolutionErp.Domain.Common;
 using SolutionErp.Domain.Contracts;   // reuse WorkflowApproverKind
+using SolutionErp.Domain.Identity;     // reuse PositionLevel
 
 namespace SolutionErp.Domain.PurchaseEvaluations;
 
@@ -34,6 +35,12 @@ public class PurchaseEvaluationWorkflowStep : BaseEntity
 
     public PurchaseEvaluationWorkflowDefinition? Definition { get; set; }
     public List<PurchaseEvaluationWorkflowStepApprover> Approvers { get; set; } = new();
+
+    // Inner steps (Mig 18) — N-stage approval cấu hình động trong cùng 1 phase.
+    // Empty list → fallback logic 2-stage Review/Confirm legacy (Mig 16) per dept.
+    // Có item → service loop theo Order: user khớp Department × PositionLevel
+    // duyệt sub-step. Tất cả required InnerSteps Done → cho phase transition.
+    public List<PurchaseEvaluationWorkflowStepInnerStep> InnerSteps { get; set; } = new();
 }
 
 public class PurchaseEvaluationWorkflowStepApprover : BaseEntity
@@ -44,3 +51,24 @@ public class PurchaseEvaluationWorkflowStepApprover : BaseEntity
 
     public PurchaseEvaluationWorkflowStep? Step { get; set; }
 }
+
+// Inner step (Mig 18 — Phase 9+) — sub-step level con cấu hình bên trong 1
+// WorkflowStep cha (= 1 phase). Cho phép admin định nghĩa thứ tự duyệt N-stage
+// theo Department × PositionLevel: NV.A → PP.A → TP.A → NV.B → PP.B → TP.B → ...
+//
+// User khớp DepartmentId + PositionLevel + Order tiếp theo chưa duyệt = approver
+// hợp lệ. CanBypassReview ở User cho TP skip NV+PP cùng dept (audit IsBypassed).
+//
+// IsRequired=false → cho phép skip không cần row approval (vd "PP optional").
+public class PurchaseEvaluationWorkflowStepInnerStep : BaseEntity
+{
+    public Guid PurchaseEvaluationWorkflowStepId { get; set; }
+    public int Order { get; set; }                              // thứ tự sequential trong cùng step cha
+    public Guid DepartmentId { get; set; }
+    public PositionLevel PositionLevel { get; set; }            // NV / PP / TP
+    public string? Name { get; set; }                            // hiển thị FE — vd "NV.PRO duyệt"
+    public int? SlaDays { get; set; }                            // override step.SlaDays nếu set
+    public bool IsRequired { get; set; } = true;                 // false → optional skip không cần row
+
+    public PurchaseEvaluationWorkflowStep? Step { get; set; }
+}