Cap the state column at 1 GB - 1 so Postgres migrates

[jpcamara]

The yrby:tables migration template set t.binary :state, limit: 4.gigabytes - 1. Postgres raises ArgumentError: No binary type has byte size 4294967295 for binary limits above 1 GB - 1 (every Rails from 7.0 through 8.1), so db:migrate on a fresh Postgres app failed — including installs arriving through gems that invoke yrby:tables. Verified against a real Postgres: the old limit raises, the new one creates bytea cleanly.

1.gigabyte - 1 is the largest limit every adapter accepts: MySQL maps anything over 16 MB to longblob (unchanged — the original value's intent), SQLite ignores limits, Postgres sits exactly at its cap. The payload column's 16 MB - 1 is under the cap and stays.

Apps that already migrated are unaffected; the generator comment and test track the new value.