Database migrations

GamePlan has two migration paths.

• A fresh installation applies 0000_baseline.sql, the complete current schema snapshot, then records the historical migration names as satisfied.
• An existing installation continues through the numbered migrations it has not yet applied. Historical files remain in the repository so an older supported database can upgrade automatically.

Never edit a migration that may already have been applied by an operator. Add a new numbered migration for every future schema change, then refresh the fresh install baseline in the same pull request. npm test verifies that the baseline contains every historical migration in order.

Before upgrading production, take a PostgreSQL backup. A failed migration is rolled back as one transaction; application rollback is safe only while its schema expectations remain compatible with the migrated database.