List signature requests

curl "https://api.craftkit.dev/v1/signatures?limit=20" \
  -H "Authorization: Bearer $CRAFTKIT_API_KEY"

{
  "signatures": [
    {
      "id": "0193c2c3-2222-7aaa-8bbb-000000000002",
      "renderId": "0193c2c3-1111-7aaa-8bbb-000000000001",
      "name": "Charter handover — BK-12345",
      "status": "completed",
      "recipients": [],
      "expirationHours": 168,
      "signedDownloadUrl": "https://api.craftkit.dev/v1/signatures/0193c2c3-2222-7aaa-8bbb-000000000002/download",
      "certificateUrl": "https://api.craftkit.dev/v1/signatures/0193c2c3-2222-7aaa-8bbb-000000000002/certificate",
      "errorMessage": null,
      "createdAt": "2026-06-05T10:00:00.000Z",
      "completedAt": "2026-06-05T11:42:08.000Z"
    }
  ],
  "nextCursor": "2026-06-05T10:00:00.000Z",
  "hasMore": false
}