feat: add Department and UserDepartment entities

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

@@ -0,0 +1,38 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  ManyToOne,
+  JoinColumn,
+  Unique,
+} from 'typeorm';
+import { User } from './user.entity';
+import { Department } from './department.entity';
+
+@Entity('user_departments')
+@Unique(['userId', 'departmentId'])
+export class UserDepartment {
+  @PrimaryGeneratedColumn()
+  id: number;
+
+  @Column({ name: 'user_id', type: 'integer' })
+  userId: number;
+
+  @ManyToOne(() => User, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'user_id' })
+  user: User;
+
+  @Column({ name: 'department_id', type: 'integer' })
+  departmentId: number;
+
+  @ManyToOne(() => Department, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'department_id' })
+  department: Department;
+
+  @Column({ name: 'is_default', type: 'boolean', default: false })
+  isDefault: boolean;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+}