Baseline integration test suite using Playwright or Puppeteer

[busbyk]

We should establish a basic but relatively thorough integration test suite using Playwright or Puppeteer. I primarily want this for knowing if I've broken something after making a change so maybe we build this out as a regression test suite initially.

I'm thinking basic functionality checks like:

• user can log in
• user can visit the posts collection list
• user can create a new post
• user can delete a post
• user can edit a post

We could start with just testing the Payload admin panel and test basics for a couple roles like super admin, single tenant admin, provider manager, provider.

This sounds like a lot but once we establish a pattern we can use Claude to build out the full suite.

We can take a look at Payload's test suite for inspiration on approach here too. test dir relevant docs from their contributing.md