Switch to Puma for development server

[nimmolo]

This switches dev servers to run Puma instead of Webrick, bringing our dev environment a bit closer to production. @mo-nathan says he uses it at work, and seems smooth.

Puma is also the easiest way to run action cable in dev, but i wanted to merge this separately (ahead of #2107) to catch any potential issues.

Please test by running rails s on this branch. You should get something like this:

=> Booting Puma
=> Rails 7.1.3.2 application starting in development 
=> Run `bin/rails server --help` for more startup options
Puma starting in single mode...
* Puma version: 6.4.2 (ruby 3.3.0-p0) ("The Eagle of Durango")
*  Min threads: 1
*  Max threads: 1
*  Environment: development
*          PID: 85550
* Listening on http://127.0.0.1:3000
* Listening on http://[::1]:3000
* Starting control server on unix:///var/folders/qp/jnsw6x194nsd2fl9g91648240000gn/T/puma-status-1714705883016-85550

Debug should work as currently.

I can't remember if other steps are required, but I don't believe so. I didn't make any changes in my config/database.yml in any case.

[coveralls]

coverage: 94.446%. remained the same when pulling c58e2d7b797169f135017164e70d4c12c37728da on nimmo-puma-local into 5cbb901148050ee08b83ef7fde6a518b51125070 on main.