The frontend was blocking week close until every workday had a
closed_days record, which no longer matches the backend's rules
(untracked days are implicitly 0h). Replace the all-workdays-closed
guard with a simple check: week has started (Monday ≤ today) and
is not already closed. The server returns a clear error if a day
with entries still needs closing.
Also fixes a pre-existing TS type narrowing error on currentSettings
and removes the now-unused .hint CSS rule.
