feat: add source tracking fields to Department for sync idempotency

apps/server/src/entities/department.entity.ts

@@ -41,6 +41,15 @@ export class Department {
   @Column({ length: 20, default: 'active' })
   status: string;
 
+  @Column({ length: 20, nullable: true })
+  source: string;
+
+  @Column({ name: 'source_id', length: 50, nullable: true })
+  sourceId: string;
+
+  @Column({ name: 'parent_source_id', length: 50, nullable: true })
+  parentSourceId: string;
+
   @CreateDateColumn({ name: 'created_at' })
   createdAt: Date;