Add bun-postgres-runtime

[djgrant]

Summary

• add PostgreSQL-based runtime package
• implement DAOs and event loop using Bun.sql
• provide tests covering the new runtime
• relax some timing expectations in async and cache tests
• wire package into tsconfig references
• handle absence of PostgreSQL in CI tests
• fix postgres runtime tests
• improve coverage for Postgres task queue, scheduler, and timers

Testing

• pnpm install
• bun test packages/bun-postgres-runtime/src/postgres-runtime.test.ts
• bun test

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https://chatgpt.com/codex/tasks/task_e_6841ba1d0a108321930f1feae790f36b