Now that only the manager sets start_date, and only at the moment of
approval (which immediately activates the campaign), a draft campaign
can never have a start_date. This made three things permanently
unreachable: the hourly _run_scheduled_campaign_activation cron job,
the activate_campaign 409/force future-date guard, and a query filter
hiding tests from scheduled-but-inactive draft campaigns. Removes all
three rather than leaving dead code behind. Also adds the missing
manager-cannot-directly-activate router test.
Moves the local _post cookie-clearing helper into a shared 'api' fixture
in conftest.py so later router tests in this plan (Tasks 10/11) don't
have to reinvent or forget the TestClient cookie-vs-Authorization-header
gotcha. Also adds a one-line comment at both require_any_role("manager")
call sites clarifying admin passthrough is automatic.
kitos