[CLAUDE] PurchaseEvaluation: Chunk B Service V2 hook UPSERT opinion + DTO + GET include

Service `ApproveV2Async` sau khi log approval (Decision=Approve) → UPSERT
row `PurchaseEvaluationLevelOpinions` cho Cấp hiện tại (auto sync ý kiến
từ comment khi duyệt). Reject KHÔNG sync.

Match level theo ApproverUserId của actor (multi-NV cùng Cấp OR-of-N).
Admin override (actor.Id KHÔNG match) → fallback first level — FE detect
SignedByUserId !== Level.ApproverUserId hiển thị "Admin duyệt thay".

Empty/whitespace comment → "(duyệt — không ý kiến)" placeholder (Q4 bonus).

Helper `ResolveActorFullNameAsync(actorUserId, isSystem, ct)` lookup
denorm SignedByFullName từ Users (fallback "(System)" / "(unknown)").

DTO `PurchaseEvaluationLevelOpinionDto` (15 fields):
- StepOrder/StepName/StepDepartmentId/StepDepartmentName (Bước Phòng)
- LevelOrder/LevelName/ApproverUserId/ApproverFullName (Cấp NV)
- Comment/SignedAt/SignedByUserId/SignedByFullName (sign-off)

GetPurchaseEvaluationQueryHandler:
- Include LevelOpinions
- helper BuildLevelOpinionsAsync JOIN ApprovalWorkflows.Steps.Levels +
  Departments + Users → denorm DTO. Empty list cho phiếu V1 / V2 chưa
  có cấp nào duyệt → FE fallback message.

Verify: dotnet build pass + dotnet test 81 pass (no regression).

Chunk C kế tiếp: FE Section 5 dynamic mirror 2 app.

src/Backend/SolutionErp.Infrastructure/Services/PurchaseEvaluationWorkflowService.cs

@@ -187,6 +187,42 @@ public class PurchaseEvaluationWorkflowService(
             ApprovedAt = dateTime.UtcNow,
         });
 
+        // Mig 26 (Session 19) — UPSERT opinion vào row Level chính chủ. Section 5
+        // FE render dynamic theo flow.steps[].levels[]. Q1=1B chốt: comment khi
+        // duyệt auto sync sang Section 5 (read-only summary). Empty comment →
+        // "(duyệt — không ý kiến)" placeholder Q4 bonus.
+        // Multi-NV cùng Cấp (OR-of-N): match level theo ApproverUserId. Admin
+        // override → fallback first level group; FE detect SignedByUserId !==
+        // Level.ApproverUserId → banner "Admin duyệt thay".
+        var matchingLevel = pendingLevelGroup.FirstOrDefault(l => actorUserId.HasValue && l.ApproverUserId == actorUserId.Value)
+                            ?? pendingLevelGroup.First();
+        var actorFullName = await ResolveActorFullNameAsync(actorUserId, isSystem, ct);
+        var existingOpinion = await db.PurchaseEvaluationLevelOpinions
+            .FirstOrDefaultAsync(o => o.PurchaseEvaluationId == evaluation.Id
+                && o.ApprovalWorkflowLevelId == matchingLevel.Id, ct);
+        var normalizedComment = string.IsNullOrWhiteSpace(comment)
+            ? "(duyệt — không ý kiến)"
+            : comment.Trim();
+        if (existingOpinion is null)
+        {
+            db.PurchaseEvaluationLevelOpinions.Add(new PurchaseEvaluationLevelOpinion
+            {
+                PurchaseEvaluationId = evaluation.Id,
+                ApprovalWorkflowLevelId = matchingLevel.Id,
+                Comment = normalizedComment,
+                SignedAt = dateTime.UtcNow,
+                SignedByUserId = actorUserId ?? Guid.Empty,
+                SignedByFullName = actorFullName,
+            });
+        }
+        else
+        {
+            existingOpinion.Comment = normalizedComment;
+            existingOpinion.SignedAt = dateTime.UtcNow;
+            existingOpinion.SignedByUserId = actorUserId ?? Guid.Empty;
+            existingOpinion.SignedByFullName = actorFullName;
+        }
+
         // Advance: nếu còn cấp tiếp trong Step → levelOrder++; else → next Step + level 1
         if (currentLevelOrder < maxLevelOrder)
         {
@@ -353,4 +389,18 @@ public class PurchaseEvaluationWorkflowService(
                 ct: ct);
         }
     }
+
+    // Mig 26 (Session 19) — helper resolve FullName cho denorm `SignedByFullName`.
+    // System auto-approve (actorUserId null + isSystem) → "(System)". User không
+    // tồn tại / xóa → fallback UserName / "(unknown)".
+    private async Task<string> ResolveActorFullNameAsync(Guid? actorUserId, bool isSystem, CancellationToken ct)
+    {
+        if (isSystem || actorUserId is null) return "(System)";
+        var user = await db.Users.AsNoTracking()
+            .Where(u => u.Id == actorUserId.Value)
+            .Select(u => new { u.FullName, u.UserName })
+            .FirstOrDefaultAsync(ct);
+        if (user is null) return "(unknown)";
+        return !string.IsNullOrWhiteSpace(user.FullName) ? user.FullName : (user.UserName ?? "(unknown)");
+    }
 }