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/CreateProjectForm.tsx

@@ -0,0 +1,85 @@
+'use client';
+
+import { useState, type FormEvent } from 'react';
+import { useRouter } from 'next/navigation';
+
+export function CreateProjectForm() {
+  const router = useRouter();
+  const [name, setName] = useState('');
+  const [description, setDescription] = useState('');
+  const [error, setError] = useState<string | null>(null);
+  const [loading, setLoading] = useState(false);
+
+  async function onSubmit(event: FormEvent<HTMLFormElement>) {
+    event.preventDefault();
+    setLoading(true);
+    setError(null);
+
+    const res = await fetch('/api/projects', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ name, description: description || undefined }),
+    });
+
+    if (res.ok) {
+      const data = (await res.json()) as { project: { id: number } };
+      router.push(`/projects/${data.project.id}`);
+      return;
+    }
+
+    const body = (await res.json().catch(() => null)) as {
+      error?: { message?: string };
+    } | null;
+    setError(body?.error?.message ?? 'プロジェクトの作成に失敗しました');
+    setLoading(false);
+  }
+
+  return (
+    <form
+      onSubmit={onSubmit}
+      className="flex flex-col gap-2 rounded-lg border bg-white p-4 shadow-sm sm:flex-row sm:items-end"
+    >
+      <div className="flex-1">
+        <label htmlFor="project-name" className="block text-sm font-medium">
+          プロジェクト名
+        </label>
+        <input
+          id="project-name"
+          type="text"
+          value={name}
+          onChange={(e) => setName(e.target.value)}
+          className="mt-1 w-full rounded border px-3 py-2"
+          required
+          maxLength={200}
+        />
+      </div>
+      <div className="flex-1">
+        <label
+          htmlFor="project-description"
+          className="block text-sm font-medium"
+        >
+          説明（任意）
+        </label>
+        <input
+          id="project-description"
+          type="text"
+          value={description}
+          onChange={(e) => setDescription(e.target.value)}
+          className="mt-1 w-full rounded border px-3 py-2"
+        />
+      </div>
+      <button
+        type="submit"
+        disabled={loading}
+        className="rounded bg-blue-600 px-4 py-2 font-medium text-white hover:bg-blue-700 disabled:opacity-50"
+      >
+        {loading ? '作成中...' : '新規プロジェクト'}
+      </button>
+      {error && (
+        <p className="text-sm text-red-600 sm:full" role="alert">
+          {error}
+        </p>
+      )}
+    </form>
+  );
+}