tests: prove query state is ledger-derived and rebuildable

[Ayush3941]

Summary

Adds ledger-derived-state coverage for gateway persistence.

Verifies that gateway state is rebuildable from committed ledger history by checking that:

• the gateway query store contains only ledger-derived user tables
• the same ledger-derived block data reproduces the same query results in a fresh store
• local gateway state can be discarded and rebuilt from committed ledger history with the same result

Refs #66.

Test plan

• gofmt -l .
• go vet $(go list ./... | grep -v '/integration')
• go tool staticcheck ./...
• go test -count=1 $(go list ./... | grep -v '/integration')