No indicator for token registry service status

[linconvidal]

Context & versions

• Feature: Token Registry integration (v1.4.0)
• Network: All networks
• Config: TOKEN_REGISTRY_ENABLED=true, external metadata server

Actual behavior

• Token registry runs as separate external service (cf-token-metadata-registry)
• Rosetta API has no visibility into registry service status:
  • Can't detect if registry server is configured/running
  • Can't detect if registry server is accessible
  • Can't detect if registry data is synced
• Users can query registry API directly, but not through Rosetta API
• /network/status only shows blockchain sync, ignores registry
• No way to distinguish: "registry not synced" vs "registry unreachable" vs "token not registered" vs "registry disabled"

Expected behavior

Rosetta spec supports stage field in SyncStatus to indicate sync phases. Should expose registry status:

{
  "sync_status": {
    "current_index": 5432,
    "target_index": 8000,
    "stage": "token metadata sync",
    "synced": false
  }
}

Proposed stages:

• "blockchain sync" - initial chain sync
• "token metadata sync" - registry syncing/unreachable
• "synced" or omit - all services ready