Mirrors the team filter just added to /workers/. WorkLog.team is a
nullable FK, so the filter accepts:
- empty → all logs (default)
- digit → logs tagged with that team
- 'none' → logs with no team set (ad-hoc attendance)
Filter row reflowed to col-md-3 col-lg-2 so all four selects fit on
a single row on wide screens; mobile stacks them. CSV export link
now passes &team=… through. Supervisors only see teams they
supervise in the dropdown.
4 regression tests covering filter narrowing, no-team match,
empty=show-all, and filter_params round-trip for the List/Calendar
toggle links.