Optimize RPC usage

[fr1jo]

Summary

• enable ethers JSON-RPC batching and optional RPC method counting
• add run-scoped memoization, Multicall3, and immutable historical RPC caching
• reduce redundant Tractor, inflow, season-seeder, and timestamp lookup RPC reads
• add focused tests for multicall, RPC cache, inflow memoization, and season seeding

Validation

• npm test -- --runInBand
• git diff --check
• live local indexer smoke run with LOG_RPC=1 completed after fixes

Deployment Notes

• no database migration in this patch
• no public API route or response-shape change intended
• production deploy is triggered by merge to main via GitHub Actions SSH deploy workflow
• recommended first step is manual dev deployment from this branch, then compare key API endpoints before merging