feat(manage): 实现部门负责人视角，支持只读查看部门成员项目与任务

部门负责人/部门管理员可通过系统配置开启，选择管理部门后只读查看
本部门及下级部门成员的全部项目和任务。前端自动根据 department_readonly
标记禁用编辑操作，后端统一注入负责人视角上下文控制数据访问边界。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Http/Controllers/Api/SystemController.php

@@ -94,6 +94,7 @@ class SystemController extends AbstractController
                     'unclaimed_task_reminder',
                     'unclaimed_task_reminder_time',
                     'task_ai_auto_analyze',
+                    'department_owner_project_view',
                 ])) {
                     unset($all[$key]);
                 }
@@ -148,6 +149,7 @@ class SystemController extends AbstractController
         $setting['unclaimed_task_reminder'] = $setting['unclaimed_task_reminder'] ?: 'close';
         $setting['unclaimed_task_reminder_time'] = $setting['unclaimed_task_reminder_time'] ?: '';
         $setting['task_ai_auto_analyze'] = $setting['task_ai_auto_analyze'] ?: 'open';
+        $setting['department_owner_project_view'] = $setting['department_owner_project_view'] ?: 'close';
         $setting['server_timezone'] = config('app.timezone');
         $setting['server_version'] = Base::getVersion();
         //