Handle pruned historical state in Augurscan

[KillariDev]

Summary

• treat permanent Reth historical-state pruning during eth_getCode as unavailable history instead of absent contract code
• fall back to conservative log coverage without entering lifecycle failure backoff
• cache unavailable addresses for the current indexer process and keep periodic deployment discovery moving to later candidates
• preserve full RPC exchange logging while reporting expected pruning as a warning
• keep transient RPC and block-header failures retryable and uncached

Root cause

Deployment discovery translated pruned historical bytecode reads into a false no-code result. That could bisect toward the RPC retention boundary, omit relevant log history, and allow the error to surface through repeated indexer work. RPC diagnostics also reported every JSON-RPC error at error severity before the deployment layer classified it.

Validation

• bun run tsc
• cd augurScan && bun run test:unit — 252 passed
• cd augurScan && bun run check
• cd augurScan && bun run test:integration — 9 passed, 3 skipped because POSTGRES_TEST_URL was unavailable
• bun run check:changed
• git diff --check origin/main...HEAD

Final read-only review: 98/100, no High, Medium, or Low findings.