ryanmcdonough closes a hole in who can touch your projects

The chat-creation endpoint trusted whatever project a request named, and wrote the new chat against it without checking whether the person actually had access to that project. So a logged-in user could point a new chat at any project they knew existed and slip past the sharing controls entirely - even projects they'd never been granted visibility into.

The fix adds the same access check the rest of the codebase already runs everywhere else; this one path had simply been missed. If you don't have access, the system now refuses, and - by deliberate convention - won't even confirm the project exists, so it gives nothing away to a prying caller. The upstream version of Mike still has the gap open.