fix: system management module - add dept/permission delete api, role assignment update, null-safety fixes

src/main/java/com/freedom/admin/entity/TSysUser.java

@@ -90,5 +90,11 @@ public class TSysUser implements Serializable {
      */
     private Boolean delFlag;
 
+    /**
+     * 角色ID集合（非表字段，用于列表回显）
+     */
+    @com.baomidou.mybatisplus.annotation.TableField(exist = false)
+    private String roleIds;
+
     private static final long serialVersionUID = 1L;
 }