feat(m14): backup & admin (zip via fflate, admin guard, tests, e2e)

- BackupService (admin-only: createBackup zips DB+uploads via fflate to
  backups/backup-<ts>.zip, listBackups newest-first, getBackupPath with
  path-traversal guard)
- Admin backup APIs: GET/POST /api/admin/backups, GET /api/admin/backups/:filename
- Admin backups screen (admin-only) + BackupCreateButton
- Playwright globalSetup seeds a system_admin user for admin E2E
- add fflate dependency
- Unit tests (BackupService: zip content, list, admin guard, traversal) +
  e2e backup (create/list/download + non-admin 403)

tests/e2e/globalSetup.ts

@@ -0,0 +1,34 @@
+import bcrypt from 'bcrypt';
+import fs from 'node:fs';
+import path from 'node:path';
+import { SqliteDatabase } from '@/lib/db/sqlite';
+import { Migrator } from '@/lib/db/migrator';
+import { UserRepository } from '@/repositories/UserRepository';
+
+const ADMIN_EMAIL = 'admin@example.com';
+const ADMIN_PASSWORD = 'admin123';
+
+/**
+ * E2E用の初期データをセットアップする。
+ * - Migrationを確実に適用(開発サーバのmigrateと重複しても冪等)
+ * - バックアップ/管理者機能のE2Eで使用する system_admin ユーザーを生成
+ */
+export default async function globalSetup(): Promise<void> {
+  const dbPath = process.env.SQLITE_PATH ?? './data/app.db';
+  fs.mkdirSync(path.dirname(dbPath), { recursive: true });
+
+  const db = new SqliteDatabase(dbPath);
+  const migrationsDir = path.join(process.cwd(), 'lib', 'db', 'migrations');
+  new Migrator(db, migrationsDir).migrate();
+
+  const userRepo = new UserRepository(db);
+  if (!userRepo.findByEmail(ADMIN_EMAIL)) {
+    userRepo.create({
+      name: 'Admin',
+      email: ADMIN_EMAIL,
+      passwordHash: bcrypt.hashSync(ADMIN_PASSWORD, 10),
+      role: 'system_admin',
+    });
+  }
+  db.close();
+}