feat: relayer RPC failover

[N-thnI]

Description
Add multi-RPC support.

Problem Statement
Node downtime risk.

Technical Requirements

• Provider rotation.

Implementation Guide

• Suggested Approach: Round-robin logic.
• Affected Areas: src/

Acceptance Criteria

• Engine switches nodes.

Security & Audit Considerations

• None.

Definition of Done

• Node health check.

[Achievers-sketch]

Experienced with blockchain infrastructure and RPC integrations. I can implement failover, health checks, provider rotation, testing, and reliability.

[grantfox-oss]

🦊 GrantFox — @Achievers-sketch has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #21)
2. Your PR will be reviewed by the Vero-protocol maintainers

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