feat: shutdown drain, reorg rollback, startup config and rpc breaker

[10xwhoman]

Summary

This pull request resolves 4 core testnet launch, indexer resilience, and configuration issues:

1. Graceful Shutdown Drain Verification (testnet: verify graceful shutdown against staging under real load #500):

   • Verified shutdown drain timing, SSE client clean reconnection with Last-Event-ID, and safe cursor commit before exit.
   • Tuned termination grace periods to exceed measured drain times.

2. Reorg Rollback Handling & Consistency (testnet: prove reorg handling against a real testnet rollback #504):

   • Proved reorg detection, cursor rewind to the fork point, and orphaned ledger event pruning with regression test coverage.

3. Startup Configuration Validation (testnet: validate indexer configuration at startup with clear fatal errors #509):

   • Enforced fail-fast startup validation for required RPC endpoints, database URLs, and network parameters.

4. RPC Failure Backoff & Circuit Breaker (testnet: backoff with jitter and a circuit breaker for RPC failures #510):

   • Added exponential backoff with jitter and circuit breaker state tracking to prevent cascading failures during RPC outages.

Linked Issues

• Closes testnet: verify graceful shutdown against staging under real load #500
• Closes testnet: prove reorg handling against a real testnet rollback #504
• Closes testnet: validate indexer configuration at startup with clear fatal errors #509
• Closes testnet: backoff with jitter and a circuit breaker for RPC failures #510

[drips-wave]

@10xwhoman Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits