Each provider page (avito/cian/yandex) now has identical structure via a
shared <ScraperPage source> component: trigger/запуск, runs-log/очередь
(per-source city-sweep runs + cancel), cron-расписание, and a per-source
request delay — каждый скраппер своя задержка.
Add /scrapers hub with global delay (lower-bound for all) + schedules
summary table (enable/disable + next_run across all sources) + provider
cards. Move cian-cookies (DMIR_AUTH upload + test-auth) into a section on
the cian page; old /scrapers/cian-cookies route now client-redirects.
Topbar gains a Скрапперы hub link.
Backend cian/yandex city-sweep endpoints already exist on main (#860/#867).
No backend changes in this PR — frontend-only unification.
