Add audit event backed TIPS routes

[niran]

Summary

• add an audit-archiver JSON-RPC client for Postgres transaction event queries
• switch block, bundle, transaction, and rejected API routes to audit-backed mode behind TIPS_UI_QUERY_BACKEND=audit
• adapt audit event responses back into the existing route shapes so the UI can keep using the current contracts during rollout
• add adapter coverage for the old-mode flag and new-mode response shaping

Notes

• S3 remains the default route backend unless TIPS_UI_QUERY_BACKEND=audit is set.
• This PR reflects the current transaction-events-query worktree state; subsequent workstream agents may layer additional changes on top.

Verification

• npm run lint
• npx tsc --noEmit

npm run lint passes with the existing warning in src/app/block/[hash]/page.tsx about an opaque any cast.