Use PGlite for generated db:generate

[TBSKR]

Fixes #2

@algora-pbc /claim #2

Summary

• updates the scaffolded db:generate script to run pgstrap generate --pglite, so generated projects can produce types without a background Postgres server
• keeps direct pgstrap generate behavior pointed at the configured Postgres database for compatibility
• restores DATABASE_URL and closes temporary PGlite/gateway resources even when generation fails
• adds a regression test for the failure cleanup path

Verification

• npx --yes bun@latest run format:check
• npx --yes bun@latest test
• npx --yes bun@latest run build