[CLAUDE] Domain+App+Api: Module Ngan sach (Budget) - 4 bang + workflow simple

User request: 'Them cho tao 4 bang luu ve ngan sach: Header / Chi tiet
/ Quy trinh duyet / Lich su thay doi'.

Domain (5 file + 1 enum):
 - Budget (header) — Aggregate root, AuditableEntity. Field: MaNganSach,
   TenNganSach, Description, NamNganSach, ProjectId FK, DepartmentId?,
   DrafterUserId, Phase (BudgetPhase 5-state), TongNganSach (sum auto
   tu Details), SlaDeadline, SlaWarningSent.
 - BudgetDetail — flat row pattern (GroupCode/GroupName + Item +
   KhoiLuong/DonGia/ThanhTien). 18,4 precision KhoiLuong, 18,2 money.
 - BudgetApproval — workflow history (FromPhase/ToPhase/Decision/Comment)
 - BudgetChangelog — audit log unified (EntityType: Header/Detail/Workflow)
 - BudgetPhase enum 5 state: DangSoanThao(1) → ChoCCM(2) → ChoCEO(3) →
   DaDuyet(4) | TuChoi(99)
 - BudgetPolicy hardcoded (no versioned WF, simple default per user
   confirm 'tam thoi don gian'): Drafter/DeptManager → CCM → CEO/
   AuthorizedSigner. Reject path back to DangSoanThao.

Migration 14 AddBudgets:
 - 4 bang moi: Budgets + BudgetDetails + BudgetApprovals + BudgetChangelogs
 - Index: Phase+IsDeleted, ProjectId, NamNganSach, SlaDeadline,
   MaNganSach unique filtered. Cascade delete child.
 - +2 cot FK ngoai bang (per user 'lien ket ca 3'):
   * Contracts.BudgetId Guid? + index
   * PurchaseEvaluations.BudgetId Guid? + index
   Cho phep doi chieu chi phi HD/PE vs ngan sach goi thau.

Application CQRS (BudgetFeatures.cs ~340 line):
 - CreateBudget + UpdateBudgetDraft + TransitionBudget + ListBudgets
   (filter Phase/Project/Year + search + paging) + GetBudget bundle
   (Header + Details + Approvals + Workflow summary)
 - DeleteBudget (only DangSoanThao/TuChoi)
 - AddBudgetDetail + UpdateBudgetDetail + DeleteBudgetDetail (auto
   recompute TongNganSach = sum Details.ThanhTien)
 - ListBudgetChangelogs

Api: BudgetsController 11 endpoint REST /api/budgets:
 - GET /  /{id}  /{id}/changelogs
 - POST /  /{id}/transitions  /{id}/details
 - PUT /{id}  /{id}/details/{detailId}
 - DELETE /{id}  /{id}/details/{detailId}

DbContext + IApplicationDbContext: 4 DbSet new (Budgets/Details/
Approvals/Changelogs).

MenuKeys + DbInitializer: 4 menu key (Budgets root + Bg_List/Create/
Pending leaves) seed dau order=27 'Ngan sach' icon Wallet. Auto-grant
admin permission via SeedAdminPermissionsAsync (MenuKeys.All).

MaNganSach format don gian 'NS-YYYYMM-NNNN' Random.Shared (chua atomic
sequence - user said 'tam thoi chua co').

Workflow chua versioned, hardcode BudgetPolicy.Default. Tuong lai admin
config qua UI: them BudgetWorkflowDefinition tables tuong tu PE.

src/Backend/SolutionErp.Domain/Budgets/Budget.cs

@@ -0,0 +1,29 @@
+using SolutionErp.Domain.Common;
+
+namespace SolutionErp.Domain.Budgets;
+
+// Aggregate root quản lý ngân sách. Gắn với Project (required), reference
+// từ PurchaseEvaluation + Contract (cả 2 nullable FK Budget.Id).
+//
+// Workflow đơn giản 3-step: Drafter → CCM → CEO. Pattern hardcoded trong
+// BudgetPolicy (chưa versioned, tương lai có thể thêm BudgetWorkflowDefinition
+// nếu cần admin config).
+public class Budget : AuditableEntity
+{
+    public string? MaNganSach { get; set; }                  // Auto-gen NS-YYYYMM-XXXX
+    public string TenNganSach { get; set; } = string.Empty;
+    public string? Description { get; set; }
+    public int NamNganSach { get; set; }                     // Năm áp dụng (vd 2026)
+    public Guid ProjectId { get; set; }                      // FK Projects (required)
+    public Guid? DepartmentId { get; set; }
+    public Guid? DrafterUserId { get; set; }
+
+    public BudgetPhase Phase { get; set; } = BudgetPhase.DangSoanThao;
+    public decimal TongNganSach { get; set; }                // Tổng = sum BudgetDetails.ThanhTien (computed)
+    public DateTime? SlaDeadline { get; set; }
+    public bool SlaWarningSent { get; set; }
+
+    public List<BudgetDetail> Details { get; set; } = new();
+    public List<BudgetApproval> Approvals { get; set; } = new();
+    public List<BudgetChangelog> Changelogs { get; set; } = new();
+}

src/Backend/SolutionErp.Domain/Budgets/BudgetApproval.cs

@@ -0,0 +1,17 @@
+using SolutionErp.Domain.Common;
+using SolutionErp.Domain.Contracts;   // reuse ApprovalDecision
+
+namespace SolutionErp.Domain.Budgets;
+
+public class BudgetApproval : BaseEntity
+{
+    public Guid BudgetId { get; set; }
+    public BudgetPhase FromPhase { get; set; }
+    public BudgetPhase ToPhase { get; set; }
+    public Guid? ApproverUserId { get; set; }                // null = system SLA auto
+    public ApprovalDecision Decision { get; set; }
+    public string? Comment { get; set; }
+    public DateTime ApprovedAt { get; set; }
+
+    public Budget? Budget { get; set; }
+}

src/Backend/SolutionErp.Domain/Budgets/BudgetChangelog.cs

@@ -0,0 +1,28 @@
+using SolutionErp.Domain.Common;
+using SolutionErp.Domain.Contracts;   // reuse ChangelogAction
+
+namespace SolutionErp.Domain.Budgets;
+
+// Audit log unified cho mọi thay đổi trên ngân sách.
+public class BudgetChangelog : BaseEntity
+{
+    public Guid BudgetId { get; set; }
+    public Budget? Budget { get; set; }
+
+    public BudgetEntityType EntityType { get; set; }
+    public Guid? EntityId { get; set; }
+    public ChangelogAction Action { get; set; }
+    public BudgetPhase? PhaseAtChange { get; set; }
+    public Guid? UserId { get; set; }
+    public string? UserName { get; set; }
+    public string? Summary { get; set; }
+    public string? FieldChangesJson { get; set; }
+    public string? ContextNote { get; set; }
+}
+
+public enum BudgetEntityType
+{
+    Header = 1,
+    Detail = 2,
+    Workflow = 3,
+}

src/Backend/SolutionErp.Domain/Budgets/BudgetDetail.cs

@@ -0,0 +1,22 @@
+using SolutionErp.Domain.Common;
+
+namespace SolutionErp.Domain.Budgets;
+
+// Chi tiết ngân sách — pattern flat row giống PurchaseEvaluationDetail.
+// Group A.I/A.II/... cho hạng mục cha, NoiDung cho item con.
+public class BudgetDetail : BaseEntity
+{
+    public Guid BudgetId { get; set; }
+    public string GroupCode { get; set; } = string.Empty;    // "A.I", "A.II", ...
+    public string GroupName { get; set; } = string.Empty;    // "Bê tông", "Phụ gia", ...
+    public string? ItemCode { get; set; }
+    public string NoiDung { get; set; } = string.Empty;
+    public string? DonViTinh { get; set; }
+    public decimal KhoiLuong { get; set; }
+    public decimal DonGia { get; set; }
+    public decimal ThanhTien { get; set; }                   // = KhoiLuong × DonGia (hoặc nhập tay)
+    public int Order { get; set; }
+    public string? GhiChu { get; set; }
+
+    public Budget? Budget { get; set; }
+}

src/Backend/SolutionErp.Domain/Budgets/BudgetPhase.cs

@@ -0,0 +1,14 @@
+namespace SolutionErp.Domain.Budgets;
+
+// State machine ngân sách — đơn giản 3 bước duyệt + 2 terminal.
+//   DangSoanThao → ChoCCM → ChoCEO → DaDuyet
+//   Bất kỳ phase duyệt → DangSoanThao (reject)
+//   DangSoanThao → TuChoi
+public enum BudgetPhase
+{
+    DangSoanThao = 1,
+    ChoCCM = 2,
+    ChoCEO = 3,
+    DaDuyet = 4,
+    TuChoi = 99,
+}

src/Backend/SolutionErp.Domain/Budgets/BudgetPolicy.cs

@@ -0,0 +1,63 @@
+using SolutionErp.Domain.Identity;
+
+namespace SolutionErp.Domain.Budgets;
+
+// Policy hardcoded đơn giản — chưa versioned (theo user "tạm thời simple
+// default"). Tương lai nếu admin cần config qua UI: thêm BudgetWorkflow
+// Definition tables tương tự PE workflow.
+public sealed record BudgetPolicy(
+    string Name,
+    string Description,
+    IReadOnlyDictionary<(BudgetPhase From, BudgetPhase To), string[]> Transitions,
+    IReadOnlyDictionary<BudgetPhase, TimeSpan?> PhaseSla,
+    IReadOnlyList<BudgetPhase> ActivePhases)
+{
+    public bool HasPhase(BudgetPhase phase) => ActivePhases.Contains(phase);
+
+    public bool IsTransitionAllowed(
+        BudgetPhase from, BudgetPhase to,
+        IReadOnlyList<string> actorRoles)
+    {
+        if (!Transitions.TryGetValue((from, to), out var roles)) return false;
+        return actorRoles.Any(r => roles.Contains(r));
+    }
+
+    public IReadOnlyList<BudgetPhase> NextPhasesFrom(BudgetPhase from) =>
+        Transitions.Keys.Where(k => k.From == from).Select(k => k.To).Distinct().ToList();
+}
+
+public static class BudgetPolicies
+{
+    private static readonly Dictionary<BudgetPhase, TimeSpan?> DefaultSla = new()
+    {
+        [BudgetPhase.DangSoanThao] = TimeSpan.FromDays(5),
+        [BudgetPhase.ChoCCM] = TimeSpan.FromDays(3),
+        [BudgetPhase.ChoCEO] = TimeSpan.FromDays(2),
+        [BudgetPhase.DaDuyet] = null,
+        [BudgetPhase.TuChoi] = null,
+    };
+
+    public static readonly BudgetPolicy Default = new(
+        Name: "Default",
+        Description: "Quy trình ngân sách 3-step (Drafter → CCM → CEO).",
+        Transitions: new Dictionary<(BudgetPhase, BudgetPhase), string[]>
+        {
+            [(BudgetPhase.DangSoanThao, BudgetPhase.ChoCCM)] = [AppRoles.Drafter, AppRoles.DeptManager],
+            [(BudgetPhase.DangSoanThao, BudgetPhase.TuChoi)] = [AppRoles.Drafter, AppRoles.DeptManager],
+
+            [(BudgetPhase.ChoCCM, BudgetPhase.ChoCEO)] = [AppRoles.CostControl],
+            [(BudgetPhase.ChoCCM, BudgetPhase.DangSoanThao)] = [AppRoles.CostControl],
+
+            [(BudgetPhase.ChoCEO, BudgetPhase.DaDuyet)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
+            [(BudgetPhase.ChoCEO, BudgetPhase.DangSoanThao)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
+        },
+        PhaseSla: DefaultSla,
+        ActivePhases:
+        [
+            BudgetPhase.DangSoanThao,
+            BudgetPhase.ChoCCM,
+            BudgetPhase.ChoCEO,
+            BudgetPhase.DaDuyet,
+            BudgetPhase.TuChoi,
+        ]);
+}

src/Backend/SolutionErp.Domain/Contracts/Contract.cs

@@ -23,6 +23,7 @@ public class Contract : AuditableEntity
     public DateTime? SlaDeadline { get; set; }                     // Hết hạn phase hiện tại
     public string? DraftData { get; set; }                         // JSON field values (render template)
     public bool SlaWarningSent { get; set; }                       // Flag để không gửi warning 2 lần
+    public Guid? BudgetId { get; set; }                            // Reference Budget (Phase 7) — đối chiếu chi phí HĐ vs ngân sách
 
     public List<ContractApproval> Approvals { get; set; } = new();
     public List<ContractComment> Comments { get; set; } = new();

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

@@ -51,6 +51,15 @@ public static class MenuKeys
     public const string PurchaseEvaluations = "PurchaseEvaluations";          // root group
     public const string PeWorkflows = "PeWorkflows";                           // workflow admin root
 
+    // ============================================================
+    // Module Ngân sách (Phase 7) — 4 bảng quản lý ngân sách dự án/gói thầu.
+    // 1 root + 3 leaf action (Danh sách / Thao tác / Duyệt).
+    // ============================================================
+    public const string Budgets = "Budgets";
+    public const string BudgetList = "Bg_List";
+    public const string BudgetCreate = "Bg_Create";
+    public const string BudgetPending = "Bg_Pending";
+
     public static readonly string[] PurchaseEvaluationTypeCodes =
         ["DuyetNcc", "DuyetNccPhuongAn"];
 
@@ -70,6 +79,7 @@ public static class MenuKeys
         Catalogs, CatalogUnits, CatalogMaterials, CatalogServices, CatalogWorkItems,
         Contracts, Forms, Reports,
         PurchaseEvaluations,
+        Budgets, BudgetList, BudgetCreate, BudgetPending,
         System, Users, Roles, Permissions, Workflows, PeWorkflows,
     ];
 

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

@@ -26,6 +26,7 @@ public class PurchaseEvaluation : AuditableEntity
     public string? PaymentTerms { get; set; }                        // JSON {tamUng, thanhToanTam, quyetToan, baoHanh, hanMucCongNo, danhGia}
 
     public Guid? ContractId { get; set; }                            // FK Contracts — set khi user gen HĐ từ phiếu
+    public Guid? BudgetId { get; set; }                              // FK Budget (Phase 7) — đối chiếu báo giá vs ngân sách gói thầu
 
     public List<PurchaseEvaluationSupplier> Suppliers { get; set; } = new();
     public List<PurchaseEvaluationDetail> Details { get; set; } = new();