controllers should use bespoke request DTOs instead of the `Request` service

Symfony added this feature a bit ago: https://symfony.com/blog/new-in-symfony-6-3-mapping-request-data-to-typed-objects

the LogInController uses it, but few other endpoints do. upgrade all controllers that handle requests to use them.

other notes:

• if you find a controller that really feels like "nah, it should keep using Request", add a comment explaining why Request is being used instead of a request DTO
• request DTOs must live in the same file as the controller that uses them
  • do not fall for the trap of "false sameness" - 99%+ of request DTOs have no business being shared between multiple endpoints

it's totally legit to upgrade just one endpoint or a small group of endpoints in a PR; this issue will be closed when no controllers remain which are using Request.