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

client/src/router/index.ts

@@ -30,12 +30,24 @@ const routes: RouteRecordRaw[] = [
 					title: "仪表盘"
 				}
 			},
-			// 业务模块（未开发，先使用占位页；菜单 component 落地后替换为真实组件）
+			// 业务模块
 			{
-				path: "customer",
-				name: "Customer",
-				component: () => import("@/views/Placeholder.vue"),
-				meta: { requiresAuth: true, title: "客户管理", permission: "customer:list" }
+				path: "customer/info",
+				name: "CustomerInfo",
+				component: () => import("@/views/customer/info/index.vue"),
+				meta: { requiresAuth: true, title: "客户信息", permission: "customer:list" }
+			},
+			{
+				path: "customer/department",
+				name: "CustomerDept",
+				component: () => import("@/views/customer/department/index.vue"),
+				meta: { requiresAuth: true, title: "客户部门", permission: "customer:department" }
+			},
+			{
+				path: "customer/account",
+				name: "CustomerAccount",
+				component: () => import("@/views/customer/account/index.vue"),
+				meta: { requiresAuth: true, title: "客户账号", permission: "customer:account" }
 			},
 			{
 				path: "project",