Ruff should be moved to dev dependencies

[Mulugruntz]

Describe the bug
⚠️
Note that ruff should be in dev dependencies. Otherwise you're forcing people to sync your own version of ruff. It's okayish if they don't use ruff. But if they do...

Because of this, we can no longer uv sync our codebase...

uv sync
  × No solution found when resolving dependencies:
  ╰─▶ Because openapi-python-client>=0.26.1 depends on ruff>=0.2,<0.14 and only the following versions of openapi-python-client are available:
          openapi-python-client<=0.26.1
          openapi-python-client==0.26.2
      we can conclude that openapi-python-client>=0.26.1 depends on ruff>=0.2,<0.14.
      And because foo:bar depends on openapi-python-client>=0.26.1 and foo:dev depends on ruff>=0.14, we can conclude that foo:dev and
      foo:e2e are incompatible.
      And because your project requires foo:dev and foo:bar, we can conclude that your project's requirements are unsatisfiable.

Desktop (please complete the following information):

• Python Version: 3.13.5
• openapi-python-client version 0.26.1

Additional context
Also mentioned in #1332

[dbanty]

Ruff is used in the generation process, so it's not a dev dependency. See #998 (comment)

[johnthagen]

I do humbly think we should revisit making it optional/opt-in, as it does cause resolver issues for a lot of people every time a major version of Ruff is released.