[CLAUDE] PurchaseEvaluation: demo seed 4 phieu + MaPhieu atomic sequence + Pe_* perm defaults

Polish session tiep cua PE module skeleton (commit 2c6f0ca..3990066):
3 task A (MISSING in MVP) khac STATUS.md In Progress:

1. Demo PE data seed (SeedDemoPurchaseEvaluationsAsync)
   - 4 phieu varied A/B x phase: A-001 DangSoanThao (mo), A-002
     ChoCEODuyetNCC (winner+9 quotes), A-003 DaDuyet (chua tao HD,
     PaymentTerms JSON), B-001 ChoDuAn (5-step giua chung).
   - Idempotent: skip-if-[DEMO]-exists.
   - Approval history dung policy A (3-step) hoac B (5-step).

2. MaPhieu atomic sequence — Migration 13
   - Format PE/{YYYY}/{TypeLetter}/{Seq:D3} (vd PE/2026/A/001).
   - PurchaseEvaluationCodeSequence entity (Prefix PK).
   - IPurchaseEvaluationCodeGenerator + impl SERIALIZABLE
     transaction (mirror ContractCodeGenerator 1:1).
   - Replace Random.Shared trong CreatePurchaseEvaluationCommandHandler.
   - Migration AddPurchaseEvaluationCodeSequences (1 bang).

3. Pe_* permission defaults
   - SeedPurchaseEvaluationPermissionDefaultsAsync — 7 role business x 9 menu key.
   - Drafter/DeptManager/Procurement: R+C+U; CostControl/PM/Director/AuthorizedSigner: R+U.
   - DeptManager them Delete (xoa nhap).
   - Idempotent per-(roleId x menuKey).

Build: 0 error, 2 warning (pre-existing DocxRenderer).

Files: 4 new + 8 modified (1 migration + entity + generator + DI + 2 ctx + 2 features).

Resolves: STATUS.md In Progress §A — 3 item PE MISSING.

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

src/Backend/SolutionErp.Infrastructure/Persistence/Migrations/20260424033449_AddPurchaseEvaluationCodeSequences.cs

@@ -0,0 +1,35 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace SolutionErp.Infrastructure.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddPurchaseEvaluationCodeSequences : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "PurchaseEvaluationCodeSequences",
+                columns: table => new
+                {
+                    Prefix = table.Column<string>(type: "nvarchar(100)", maxLength: 100, nullable: false),
+                    LastSeq = table.Column<int>(type: "int", nullable: false),
+                    UpdatedAt = table.Column<DateTime>(type: "datetime2", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_PurchaseEvaluationCodeSequences", x => x.Prefix);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "PurchaseEvaluationCodeSequences");
+        }
+    }
+}

src/Backend/SolutionErp.Infrastructure/Persistence/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -2165,6 +2165,23 @@ namespace SolutionErp.Infrastructure.Persistence.Migrations
                     b.ToTable("PurchaseEvaluationChangelogs", (string)null);
                 });
 
+            modelBuilder.Entity("SolutionErp.Domain.PurchaseEvaluations.PurchaseEvaluationCodeSequence", b =>
+                {
+                    b.Property<string>("Prefix")
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<int>("LastSeq")
+                        .HasColumnType("int");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("datetime2");
+
+                    b.HasKey("Prefix");
+
+                    b.ToTable("PurchaseEvaluationCodeSequences", (string)null);
+                });
+
             modelBuilder.Entity("SolutionErp.Domain.PurchaseEvaluations.PurchaseEvaluationDetail", b =>
                 {
                     b.Property<Guid>("Id")