Popovers and dropdown menus across the app (sub-address helper, calendar
toolbar/color pickers, contact/template/attachment menus, rich text editor
color and table pickers, unsubscribe confirmation, composer send menu)
were anchored with physical `left-0`/`right-0`. In RTL locales those
don't flip with the trigger, so the menu detaches from the button that
opened it. Switched to Tailwind's logical `start-0`/`end-0` (and the
matching `rounded-s-*`/`rounded-e-*` corners on hover-action overlays)
so they mirror correctly for RTL locales (ar, he, fa) while staying
identical in LTR.
