New ?team=<id> URL param narrows the worker list to that team's
members via the Team.workers M2M. ?team=none filters to workers
not assigned to any team. Default (empty) still shows all
matching workers across all teams.
UI: new "Team" dropdown in the filter row, between Search and
Status. Lists active teams alphabetically. Layout reflowed to
col-md-4 / col-md-3 / col-md-3 / col-md-2.
Konrad's checkpoint feedback: "in the worker page - can i have a
filter for teams so i can easely see who is in what team".
4 regression tests covering no-filter, by-team, no-team, and
dropdown options.
4b57cffb77