Fix populated database upgrades

[freshwax-codex]

Summary

• replace production prisma db push with versioned prisma migrate deploy
• automatically baseline installations created before Prisma migration history was introduced
• apply the release identity change as a normal migration without --accept-data-loss
• verify populated v0.0.4, previous-release, and clean-database migration paths in CI
• make migration simulation a required release-preparation check and document the new operational model

Verification

• npm run test:schema-upgrade -- v0.0.4
• npm run test:schema-upgrade -- v0.1.0
• npm run test:schema-upgrade -- --empty
• Prisma migration/schema drift check
• npm run lint
• npx prisma validate
• npx prisma generate
• npm run build
• git diff --check

Closes #33