An account refers to the user the active session is logged in as. As
such it doesn't make sense outside of the /auth API paths that deals
with the current authenticated user. Move /api/account to
/api/auth/account to reflect this.
Some functions in luxon default to the system's locale while other
functions default to "en-US". Explicitly set the locale everywhere
the luxon objects are created to avoid possible mismatches and
unexpected behaviour should the system's locale be different.
To make it possible to render the timetable in the user's local time we
need to know the timezone to render it in on the server. Otherwise
there will be hydration errors and paint flashing as the client renders
a different timezone.
Add a server global default timezone that can be overriden on a
per-account bases to prepare for timezone handling the timetable.
