refactor: 优化权限管理与登录流程，修复细节问题

1.  调整仪表盘图标从DeviceOutlined为MonitorOutlined
2.  新增403无权访问页面与路由配置
3.  完善权限存储与路由守卫逻辑
4.  修复用户信息获取与token持久化问题
5.  补充普通管理员权限初始化与补丁脚本
6.  优化后端用户服务与认证控制器逻辑
7.  调整登录表单交互与请求流程

database/fix-admin-permissions.sql

@@ -0,0 +1,28 @@
+-- ============================================================
+-- 普通管理员权限补丁 (用于已有数据库)
+-- 执行方式: 在MySQL中执行此SQL即可
+-- ============================================================
+USE smart_grid_iot;
+
+-- 给普通管理员角色(role_id=2, code='admin')分配基础管理权限
+-- 先删除已存在的(避免重复), 再插入
+DELETE FROM `role_permissions` WHERE `role_id` = 2;
+
+INSERT INTO `role_permissions` (`role_id`, `permission_id`) VALUES
+(2, (SELECT id FROM permissions WHERE code = 'dashboard')),
+(2, (SELECT id FROM permissions WHERE code = 'system')),
+(2, (SELECT id FROM permissions WHERE code = 'settings')),
+(2, (SELECT id FROM permissions WHERE code = 'user:list')),
+(2, (SELECT id FROM permissions WHERE code = 'user:create')),
+(2, (SELECT id FROM permissions WHERE code = 'user:update')),
+(2, (SELECT id FROM permissions WHERE code = 'role:list')),
+(2, (SELECT id FROM permissions WHERE code = 'system:basicSetting')),
+(2, (SELECT id FROM permissions WHERE code = 'system:securitySetting')),
+(2, (SELECT id FROM permissions WHERE code = 'log:operation'));
+
+-- 验证结果
+SELECT r.name AS 角色名称, r.code AS 角色编码, COUNT(rp.permission_id) AS 权限数量
+FROM roles r
+LEFT JOIN role_permissions rp ON r.id = rp.role_id
+WHERE r.id = 2
+GROUP BY r.id;