[CLAUDE] App+Api: PurchaseEvaluation CQRS + Controller + WorkflowService

Application (4 file, ~900 lines):
 - IPurchaseEvaluationWorkflowService + PurchaseEvaluationDtos
 - PurchaseEvaluationFeatures: Create / UpdateDraft / Transition / List /
   Inbox / GetDetail (bundle Suppliers+Details+Quotes+Approvals+Workflow) /
   Delete / ListChangelogs. IDOR filter role-based phase eligibility.
 - PurchaseEvaluationSupplierFeatures: Add / Update / Remove supplier
   (N:M Phiếu × Supplier). Block remove nếu còn Quote FK reference.
 - PurchaseEvaluationDetailFeatures: Add/Update/Delete hạng mục +
   Upsert/Delete Quote + SelectWinner (set SelectedSupplierId).

Infrastructure:
 - PurchaseEvaluationWorkflowService: policy load pinned definition →
   guard role + transition rules. Emit Notification drafter khi
   state-change. Tạo PurchaseEvaluationApproval + Changelog row.

Api:
 - PurchaseEvaluationsController ~15 endpoint: CRUD phiếu, N:M supplier,
   hạng mục CRUD, Quote upsert, SelectWinner, Changelog list.
   Route /api/purchase-evaluations.

DI: đăng ký IPurchaseEvaluationWorkflowService scoped.

Skip MVP: Attachments upload, Admin PeWorkflows designer UI (sẽ phase sau
— framework versioned WF table đã sẵn, designer pattern copy từ HĐ).

src/Backend/SolutionErp.Infrastructure/DependencyInjection.cs

@@ -6,6 +6,7 @@ using SolutionErp.Application.Common.Interfaces;
 using SolutionErp.Application.Contracts.Services;
 using SolutionErp.Application.Forms.Services;
 using SolutionErp.Application.Notifications;
+using SolutionErp.Application.PurchaseEvaluations.Services;
 using SolutionErp.Application.Reports.Services;
 using SolutionErp.Domain.Identity;
 using SolutionErp.Infrastructure.Forms;
@@ -32,6 +33,7 @@ public static class DependencyInjection
         services.AddSingleton<IDocumentConverter, LibreOfficeDocumentConverter>();
         services.AddScoped<IContractCodeGenerator, ContractCodeGenerator>();
         services.AddScoped<IContractWorkflowService, ContractWorkflowService>();
+        services.AddScoped<IPurchaseEvaluationWorkflowService, PurchaseEvaluationWorkflowService>();
         services.AddScoped<IContractExcelExporter, ContractExcelExporter>();
         services.AddScoped<INotificationService, NotificationService>();
         services.AddScoped<IChangelogService, ChangelogService>();

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

@@ -0,0 +1,133 @@
+using Microsoft.AspNetCore.Identity;
+using Microsoft.EntityFrameworkCore;
+using SolutionErp.Application.Common.Exceptions;
+using SolutionErp.Application.Common.Interfaces;
+using SolutionErp.Application.Notifications;
+using SolutionErp.Application.PurchaseEvaluations.Services;
+using SolutionErp.Domain.Contracts;
+using SolutionErp.Domain.Identity;
+using SolutionErp.Domain.Notifications;
+using SolutionErp.Domain.PurchaseEvaluations;
+
+namespace SolutionErp.Infrastructure.Services;
+
+// Mirror ContractWorkflowService. Load policy từ pinned
+// WorkflowDefinition (nếu có) hoặc fallback hardcoded registry.
+public class PurchaseEvaluationWorkflowService(
+    IApplicationDbContext db,
+    IDateTime dateTime,
+    INotificationService notifications,
+    UserManager<User> userManager) : IPurchaseEvaluationWorkflowService
+{
+    public TimeSpan? GetPhaseSla(PurchaseEvaluationPhase phase) =>
+        PurchaseEvaluationPolicies.NccOnly.PhaseSla.GetValueOrDefault(phase);
+
+    public async Task TransitionAsync(
+        PurchaseEvaluation evaluation,
+        PurchaseEvaluationPhase targetPhase,
+        Guid? actorUserId,
+        IReadOnlyList<string> actorRoles,
+        ApprovalDecision decision,
+        string? comment,
+        CancellationToken ct = default)
+    {
+        if (evaluation.Phase == targetPhase)
+            throw new ConflictException("Phiếu đã ở phase đích.");
+
+        PurchaseEvaluationPolicy policy;
+        if (evaluation.WorkflowDefinitionId is Guid wfId)
+        {
+            var def = await db.PurchaseEvaluationWorkflowDefinitions.AsNoTracking()
+                .Include(d => d.Steps.OrderBy(s => s.Order))
+                    .ThenInclude(s => s.Approvers)
+                .FirstOrDefaultAsync(d => d.Id == wfId, ct);
+            policy = def is not null
+                ? PurchaseEvaluationPolicyRegistry.FromDefinition(def)
+                : PurchaseEvaluationPolicyRegistry.ForEvaluation(evaluation);
+        }
+        else
+        {
+            policy = PurchaseEvaluationPolicyRegistry.ForEvaluation(evaluation);
+        }
+
+        var isAdmin = actorRoles.Contains(AppRoles.Admin);
+        var isSystem = actorUserId is null && decision == ApprovalDecision.AutoApprove;
+
+        if (!isAdmin && !isSystem)
+        {
+            if (!policy.Transitions.TryGetValue((evaluation.Phase, targetPhase), out var allowedRoles))
+                throw new ForbiddenException(
+                    $"Policy '{policy.Name}' không cho phép {evaluation.Phase} → {targetPhase}.");
+
+            if (!policy.IsTransitionAllowed(evaluation.Phase, targetPhase, actorRoles, actorUserId))
+            {
+                throw new ForbiddenException(
+                    $"Role ({string.Join(",", actorRoles)}) không đủ quyền chuyển {evaluation.Phase} → {targetPhase}. " +
+                    $"Policy '{policy.Name}' yêu cầu: {string.Join(",", allowedRoles)}.");
+            }
+        }
+
+        var fromPhase = evaluation.Phase;
+        evaluation.SlaWarningSent = false;
+        evaluation.Phase = targetPhase;
+
+        var sla = policy.PhaseSla.GetValueOrDefault(targetPhase);
+        evaluation.SlaDeadline = sla is null ? null : dateTime.UtcNow.Add(sla.Value);
+
+        db.PurchaseEvaluationApprovals.Add(new PurchaseEvaluationApproval
+        {
+            PurchaseEvaluationId = evaluation.Id,
+            FromPhase = fromPhase,
+            ToPhase = targetPhase,
+            ApproverUserId = actorUserId,
+            Decision = decision,
+            Comment = comment,
+            ApprovedAt = dateTime.UtcNow,
+        });
+
+        // Resolve actor name for changelog
+        string? actorName = null;
+        if (actorUserId is Guid uid)
+        {
+            var user = await userManager.FindByIdAsync(uid.ToString());
+            actorName = user?.FullName ?? user?.Email;
+        }
+
+        db.PurchaseEvaluationChangelogs.Add(new PurchaseEvaluationChangelog
+        {
+            PurchaseEvaluationId = evaluation.Id,
+            EntityType = PurchaseEvaluationEntityType.Workflow,
+            Action = ChangelogAction.Transition,
+            PhaseAtChange = targetPhase,
+            UserId = actorUserId,
+            UserName = actorName ?? "Hệ thống",
+            Summary = $"Chuyển phase {fromPhase} → {targetPhase}",
+            ContextNote = comment,
+        });
+
+        // Notify drafter
+        if (evaluation.DrafterUserId is Guid drafterId && drafterId != actorUserId)
+        {
+            var title = targetPhase switch
+            {
+                PurchaseEvaluationPhase.DaDuyet => $"Phiếu {evaluation.MaPhieu ?? evaluation.TenGoiThau} đã duyệt",
+                PurchaseEvaluationPhase.TuChoi => $"Phiếu {evaluation.TenGoiThau} bị từ chối",
+                _ => $"Phiếu {evaluation.TenGoiThau} chuyển phase mới",
+            };
+            var type = targetPhase switch
+            {
+                PurchaseEvaluationPhase.DaDuyet => NotificationType.ContractPublished,
+                PurchaseEvaluationPhase.TuChoi => NotificationType.ContractRejected,
+                _ => NotificationType.ContractPhaseTransition,
+            };
+            await notifications.NotifyAsync(
+                drafterId, type, title,
+                description: $"{fromPhase} → {targetPhase}" + (string.IsNullOrWhiteSpace(comment) ? "" : $" · {comment}"),
+                href: $"/purchase-evaluations/{evaluation.Id}",
+                refId: evaluation.Id,
+                ct: ct);
+        }
+
+        await db.SaveChangesAsync(ct);
+    }
+}