Explorer server: Add logs when receiving ledgerClosed messages and log rippled client state every 60 seconds

[kuan121]

High Level Overview of Change

Two changes

1. Log a message each time a ledgerClosed message is received.
2. Every 60 seconds, log the current state of the rippled client created via xrpl-client.

Context of Change

Although rare, we’ve observed that the Explorer server stops processing new ledger data—specifically, this log line is not printed. As a result, the metrics API endpoint begins serving stale data. The root cause is currently unclear; it could be due to a dropped WebSocket connection to the Clio host or the Clio host not sending any ledgerClosed messages. Importantly, during the incident, the Explorer backend remains up and responsive, continuing to serve API requests such as /health and /metrics (code reference).

The new logs will help us confirm the root cause if either of the above suspicions is correct, or rule them out if not.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (You added tests for code that already exists, or your new feature included in this PR)
• Documentation Updates
• Translation Updates
• Release

Codebase Modernization

• Updated files to React Hooks
• Updated files to TypeScript
• Updated tests to React Testing Library

Before / After

N/A

Test Plan

Manually test the changes by running npm run build && npm start and confirm that logs are printed as expected. An example of state log is

[2025-08-27T19:32:33.456Z]  INFO: rippled/12345 on MacBook:
    Rippled client: {
      state: {
        online: true,
        latencyMs: { last: 80, avg: 81.3, secAgo: 2.181999921798706 },
        server: {
          version: '',
          uptime: 1294403,
          publicKey: '',
          networkId: 0,
          uri: 'wss://s2.ripple.com:51233'
        },
        ledger: { last: 98451664, validated: '32570-98451664', count: 98419094 },
        fee: { last: 12, avg: 12, secAgo: 2.181999921798706 },
        reserve: { base: 1, owner: 0.2 },
        secLastContact: 1.8569998741149902
      }
    }