[codex] Optimize API RPC usage

[Brean0]

Summary

• add an RPC cost optimization port plan
• enable ethers JSON-RPC batching, optional custom RPC URLs, and RPC request counters
• add Redis-backed historical block-tag RPC caching
• collapse heavy Silo token info paths through Multicall3

Validation

• npm test -- --runInBand test/datasources/rpc-cache.test.js test/datasources/multicall.test.js test/service/silo-service.test.js
• npm test -- --runInBand

Notes

• no production deploy is triggered until this PR is merged into main