GET /v2/custodian-authorities/:id/files

List proof-of-access files uploaded for a custodian authority.

Path params:
  id (required) — Custodian-authority identifier (UUID).

Response (200 OK):
{
  "data": [
    {
      "id": "string",
      "type": "custodian-authority-file",
      "attributes": {
        "hash":       "string — algorithm-prefixed (e.g. sha2-256:...)",
        "name":       "string — logical role, e.g. power-of-attorney",
        "uploadedAt": "ISO 8601 timestamp (UTC)",
        "filename":   "string"
      }
    }
  ]
}