feat: 新增客户管理全模块功能

实现客户信息、客户部门、客户账号三个子模块的完整CRUD，包含：
1. 数据库实体、DTO、控制器、服务层代码
2. RBAC权限映射与菜单种子数据扩展
3. 前端路由与API封装
4. 数据权限隔离与鉴权逻辑
5. 配套工具脚本与测试验证清单

server/src/entity/customer_department.entity.ts

@@ -0,0 +1,68 @@
+import { Column, Model, Table, DataType, CreatedAt, UpdatedAt, BelongsTo, ForeignKey } from "sequelize-typescript";
+import Customer from "./customer.entity";
+
+@Table({
+	tableName: "customer_department",
+	comment: "客户部门表",
+	timestamps: true,
+	createdAt: "created_at",
+	updatedAt: "updated_at",
+	indexes: [
+		{ name: "idx_dept_customer", fields: ["customer_id"] }
+	]
+})
+export default class CustomerDepartment extends Model {
+	@Column({
+		type: DataType.BIGINT,
+		autoIncrement: true,
+		primaryKey: true
+	})
+	id!: number;
+
+	@ForeignKey(() => Customer)
+	@Column({
+		type: DataType.BIGINT,
+		allowNull: false,
+		field: "customer_id",
+		comment: "所属客户ID"
+	})
+	customerId!: number;
+
+	@Column({
+		type: DataType.STRING(64),
+		allowNull: false,
+		field: "dept_name",
+		comment: "部门名称"
+	})
+	deptName!: string;
+
+	@Column({
+		type: DataType.STRING(32),
+		field: "contact_person",
+		comment: "联系人"
+	})
+	contactPerson!: string;
+
+	@Column({
+		type: DataType.STRING(20),
+		field: "contact_phone",
+		comment: "联系电话"
+	})
+	contactPhone!: string;
+
+	@Column({
+		type: DataType.STRING(256),
+		field: "function_desc",
+		comment: "职能描述"
+	})
+	functionDesc!: string;
+
+	@BelongsTo(() => Customer)
+	customer!: Customer;
+
+	@CreatedAt
+	created_at!: Date;
+
+	@UpdatedAt
+	updated_at!: Date;
+}