List database branches

curl --request GET \
  --url https://api.case.dev/database/v1/projects/{id}/branches \
  --header 'Authorization: Bearer <token>'

{
  "branches": [
    {
      "id": "branch_main_123",
      "name": "main",
      "isDefault": true,
      "parentBranchId": null,
      "status": "active",
      "createdAt": "2025-01-10T08:00:00Z",
      "updatedAt": "2025-01-15T10:30:00Z"
    },
    {
      "id": "branch_staging_456",
      "name": "staging",
      "isDefault": false,
      "parentBranchId": "branch_main_123",
      "status": "active",
      "createdAt": "2025-01-12T10:00:00Z",
      "updatedAt": "2025-01-15T10:30:00Z"
    }
  ]
}