feat(m4): project & member management with tests and e2e

- ProjectRepository, ProjectMemberRepository, minimal NotificationRepository
- ProjectService: create/update/archive/delete project, add/remove member,
  permission checks (isMember/admin), member-added notification, getDashboard
  skeleton, getMyProjects, getMemberRole
- projectValidator, API services factory
- API routes: projects CRUD, members list/add/remove
- Screens: dashboard (project list + create form), project overview, members,
  settings; layout (Header/Sidebar/ProjectNav) and project components
- Unit tests (Project/ProjectMember repositories, ProjectService),
  integration project-member-permission, e2e project-management

components/layout/Header.tsx

@@ -0,0 +1,37 @@
+'use client';
+
+import { useRouter } from 'next/navigation';
+import type { PublicUser } from '@/lib/auth/getCurrentUser';
+
+export function Header({ user }: { user: PublicUser }) {
+  const router = useRouter();
+
+  async function handleLogout() {
+    await fetch('/api/auth/logout', { method: 'POST' });
+    router.push('/login');
+    router.refresh();
+  }
+
+  return (
+    <header className="flex items-center justify-between border-b bg-white px-6 py-3">
+      <a href="/dashboard" className="font-bold text-gray-800">
+        シンプルグループウェア
+      </a>
+      <nav className="flex items-center gap-4 text-sm">
+        <a href="/dashboard" className="text-gray-600 hover:underline">
+          ダッシュボード
+        </a>
+        <a href="/profile" className="text-gray-600 hover:underline">
+          {user.name} さん
+        </a>
+        <button
+          type="button"
+          onClick={handleLogout}
+          className="text-blue-600 hover:underline"
+        >
+          ログアウト
+        </button>
+      </nav>
+    </header>
+  );
+}