[CLAUDE] App+Api+FE: Chunk E5 — Budget 2-stage dept approval (mirror PE/Contract)

Budget complete the trifecta — đồng bộ pattern 2-stage cho 3 module
(Contract + PE + Budget) cùng UX cho user khi UAT.

BE App:
- TransitionBudgetCommandHandler thêm INotificationService + IDateTime DI
- Mirror logic 2-stage từ ContractWorkflowService:
  - actor.DepartmentId != null + KHÔNG admin/system + KHÔNG resume
    - DeptManager (TPB) hoặc CanBypassReview → Stage=Confirm
    - Else (NV) → Stage=Review only, BLOCK transition
  - Upsert BudgetDepartmentApproval (UNIQUE BudgetId+Phase+Dept+Stage)
  - Block khi !hasConfirm: insert Approval + Changelog + Notify TPB → return early
- BudgetDepartmentApprovalFeatures.cs (List query mirror PE/Contract)

Api:
- BudgetsController endpoint GET /budgets/{id}/department-approvals

FE (cả fe-admin + fe-user):
- types/budget.ts thêm ApprovalStage const + BudgetDepartmentApproval type
- BudgetWorkflowPanel section "Tiến trình duyệt 2-cấp phòng ban":
  - Group by phase × dept, show Review NV + Confirm TPB
  - Highlight amber "chờ TPB confirm" + badge fuchsia bypass

Note: low-priority cho Budget (ít user duyệt budget per dept) nhưng giữ
consistent UX 3 module.

Build: BE pass + FE pass cả 2 + 77 test pass.

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

src/Backend/SolutionErp.Api/Controllers/BudgetsController.cs

@@ -86,6 +86,12 @@ public class BudgetsController(IMediator mediator) : ControllerBase
     [HttpGet("{id:guid}/changelogs")]
     public async Task<List<BudgetChangelogDto>> GetChangelogs(Guid id, CancellationToken ct)
         => await mediator.Send(new ListBudgetChangelogsQuery(id), ct);
+
+    // 2-stage department approval list (Phase 9 — Migration 16).
+    [HttpGet("{id:guid}/department-approvals")]
+    public async Task<ActionResult<List<BudgetDepartmentApprovalDto>>> ListDepartmentApprovals(
+        Guid id, CancellationToken ct)
+        => Ok(await mediator.Send(new ListBudgetDepartmentApprovalsQuery(id), ct));
 }
 
 public record TransitionBudgetBody(BudgetPhase TargetPhase, ApprovalDecision Decision, string? Comment);