Resolve "Stork responsive UI"

Part of #1433 (closed)

Scope of this MR: login page, dashboard, breadcrumbs, global search, lease search view, HRs views+forms, Subnets list view + detailed tab view.

Starting from Subnets forms and everything after that in the Stork navbar menu (Shared networks, Services, Monitoring, Configuration, Help, and everything inside of those) is within the scope of !806 (merged) and following MRs.