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/project/RemoveMemberButton.tsx

@@ -0,0 +1,41 @@
+'use client';
+
+import { useState } from 'react';
+import { useRouter } from 'next/navigation';
+
+export function RemoveMemberButton({
+  projectId,
+  userId,
+  label,
+  disabled = false,
+}: {
+  projectId: number;
+  userId: number;
+  label: string;
+  disabled?: boolean;
+}) {
+  const router = useRouter();
+  const [busy, setBusy] = useState(false);
+
+  async function onRemove() {
+    setBusy(true);
+    const res = await fetch(`/api/projects/${projectId}/members/${userId}`, {
+      method: 'DELETE',
+    });
+    setBusy(false);
+    if (res.ok) {
+      router.refresh();
+    }
+  }
+
+  return (
+    <button
+      type="button"
+      onClick={onRemove}
+      disabled={disabled || busy}
+      className="text-xs text-red-600 hover:underline disabled:opacity-50"
+    >
+      {busy ? '削除中...' : label}
+    </button>
+  );
+}