Update ruby to v3.4.2

See merge request !8

This is required in order to have -dev packages available during our
build stage. Apparently, this should have never worked and the upstream
image has just been cleaned up to align with documentation.

See https://github.com/docker-library/ruby/pull/497

Closes !25

Improve conference and import management

See merge request !24

When adding a new conference, we now automatically run the import job and let the user choose relevant stages. Users can also manage relevant stages from the conference edit view.

Added tracking of import histories. The app now knows when an import has been started and ended, and errors are logged into the DB as well and exposed to the frontend.

Added an interstitial page for fetching conference data, plus a way to manually trigger imports if no data was found.

Fixup

See merge request !23

Custom data handling & dynamic import job listing

See merge request !22

Add Admin UI

See merge request !21

Add RBAC, convert existing roles

See merge request !20

Update and cleanup

See merge request !19

Update dependency selenium-webdriver to v4.28.0

See merge request !10

> This gem was aggregating the dependencies of Turbo and Stimulus,
> but offered nothing else. Aggregating dependencies is not enough
> value, so this gem is now deprecated.
> Please use the underlying frameworks directly.
(from https://github.com/hotwired/hotwire-rails)

Fixes #30

On an actual mobile it's ugly :)

Hanging indent should add some visual separation for smaller screens.

Fixes #18

Add light-gray border and some drop shadow.

Fixes #7

This functionality was lost when moving to a template-based approach for
the list of all translators.

Fixes #32

For some reason, the package is called "ruby-version"?