Production saved Starknet state from an earlier build that only knew one
Falcon account class. Its scan cursor had moved past the new backfill
snapshot, so the 20-account baseline was never applied (showing 2 instead
of 32), and blocks scanned since then missed accounts of the other five
classes.

Version the Starknet state: when the known class list or snapshot changes,
saved progress from an older version is discarded and the scan restarts
from the verified snapshot with the full class list.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

The old test could hang and never exercised the stale-round guard in OnNewBlock. TestNewBlockWatcher checks that newer rounds are stored and equal or older rounds ignored; TestNewBlockWatcherConcurrent runs readers against a writer for the race detector.

ARC-20 - Issued supply, ARC-62 extension, minors