[Bug] Schema fetch uses snapshot.indexer_url even when snapshot.enabled=false

[Mutu-s]

Describe the bug

On every startup the host tries to fetch the GraphQL schema from host.snapshot.indexer_url even when snapshot.enabled is false.

With the shipped default config.yaml, that means every install attempts:

GET http://35.206.105.60:8080/api/v1/schema

That indexer is unreachable (times out after 30s), so the host logs:

Schema fetch failed, using embedded schema: ... context deadline exceeded

and silently falls back to the embedded schema.

Root cause

pkg/host/schema_resolve.go always parses cfg.HostConfig.Snapshot.IndexerURL and never checks cfg.HostConfig.Snapshot.Enabled:

parsedURL, parseErr := url.Parse(cfg.HostConfig.Snapshot.IndexerURL)

Schema fetching is incorrectly coupled to the snapshot bootstrap config.

To Reproduce

1. Use default config.yaml (snapshot.enabled: false, indexer_url: "http://35.206.105.60:8080").
2. Start the host (Docker prod setup is enough).
3. Check logs on startup → schema fetch timeout to 35.206.105.60:8080.
4. Host continues with embedded schema.

Confirmed on production host: Docker container shinzo-host on public VPS, Aug 28 2026.

Expected behavior

When snapshot.enabled: false, the host should not call snapshot indexer_url for schema fetch.

Schema fetch should use a dedicated config (e.g. schema.indexer_url or INDEXER_SCHEMA_URL) or bootstrap/indexer discovery — not a stale snapshot default.

Impact

• Adds ~30s startup delay (HTTP client timeout) on every restart
• Operators think dynamic schema pull is working but it never succeeds on default config
• Related to [Bug] host fails to get schema from indexer with incorrect address #295 but this is the specific mis-wiring (snapshot.enabled ignored)

Suggested fix

if !cfg.HostConfig.Snapshot.Enabled {
    return schema.GetSchema() // or use dedicated schema.indexer_url when set
}

Or introduce schema.indexer_base_url separate from snapshot bootstrap.

Environment

• Image: ghcr.io/shinzonetwork/shinzo-host-client (ethereum-mainnet-latest)
• snapshot.enabled: false
• DEFRA_URL=127.0.0.1:9181