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

repositories/NotificationRepository.ts

@@ -0,0 +1,45 @@
+import type { SqliteDatabase } from '@/lib/db/sqlite';
+import type { Notification, NotificationType } from '@/lib/types';
+
+export interface CreateNotificationInput {
+  userId: number;
+  projectId: number | null;
+  type: NotificationType;
+  title: string;
+  body: string | null;
+}
+
+/**
+ * notificationsテーブルへのデータアクセスを担うRepository。
+ * M4ではメンバー追加通知のために create のみ実装する。
+ * 一覧取得・既読化は M5 で拡張する。
+ */
+export class NotificationRepository {
+  constructor(private readonly db: SqliteDatabase) {}
+
+  create(input: CreateNotificationInput): Notification {
+    const now = new Date().toISOString();
+    const result = this.db.execute(
+      `INSERT INTO notifications (user_id, project_id, type, title, body, read_at, created_at)
+       VALUES (@userId, @projectId, @type, @title, @body, NULL, @createdAt)`,
+      {
+        userId: input.userId,
+        projectId: input.projectId,
+        type: input.type,
+        title: input.title,
+        body: input.body,
+        createdAt: now,
+      }
+    );
+    return {
+      id: Number(result.lastInsertRowid),
+      userId: input.userId,
+      projectId: input.projectId,
+      type: input.type,
+      title: input.title,
+      body: input.body,
+      readAt: null,
+      createdAt: now,
+    };
+  }
+}