[Design] Add Postgres client management code

[kofi-q]

Overview

#5698

Adding (unused) postgres client lib to VsDesign for the upcoming conversion from sqlite.
Currently using the default setup and relying on the standard postgres environment variables, which are assigned accordingly in the Heroku dashboard (https://dashboard.heroku.com/apps/tmp-vxdesign-dev/settings).

Will eventually need a schema migration tool, but for now, just adding a db:reset pnpm script for dev.

Testing Plan

• Manual for now - will set up testing in upcoming PRs, when we start wiring up the store code.

Checklist

• [ ] I have added logging where appropriate to any new user actions, system updates such as file reads or storage writes, or errors introduced.

• [ ] I have added a screenshot and/or video to this PR to demo the change
• [ ] I have added the "user_facing_change" label to this PR to automate an announcement in #machine-product-updates

[kshen0]

🎉