[self-hosted][railway][prometheus] Warning: "can't collect container meta in CLOUD_UNSPECIFIED" on R

Question

Use this:

On a self-hosted Encore TypeScript app deployed on Railway, Prometheus export works, but the runtime logs this warning:

```json
{
  "message": "failed fetching container metadata: can't collect container meta in CLOUD_UNSPECIFIED, using fallback",
  "severity": "warn"
}
```

Infra config includes:

```json
{
  "metadata": {
    "app_id": "",
    "env_name": "",
    "env_type": "production",
    "cloud": "railway",
    "base_url": "https://"
  },
  "metrics": {
    "type": "prometheus",
    "collection_interval": 15,
    "remote_write_url": {
      "$env": "PROMETHEUS_REMOTE_WRITE_URL"
    }
  }
}
```

Env var:

```bash
PROMETHEUS_REMOTE_WRITE_URL=http://prometheus.railway.internal:9090/api/v1/write
```

Prometheus is running with:

```bash
/bin/prometheus --config.file=/etc/prometheus/prom.yml --storage.tsdb.path=/prometheus --web.enable-remote-write-receiver
```

Expected:
- either `metadata.cloud = "railway"` should not resolve to `CLOUD_UNSPECIFIED`
- or this fallback on unsupported/self-hosted clouds should not log at `warn`

Observed with:
- Encore CLI `v1.56.0`
- TypeScript app
- self-hosted on Railway