These popovers are portaled and positioned via inline styles computed
from getBoundingClientRect() rather than Tailwind classes, so the
logical start-0/end-0 fix doesn't reach them. They always anchored to
the physical right of their trigger (rect.right + 8), which in RTL
pushes them further into the edge the trigger is already flush against
instead of toward the visible content area.
Added isDocumentRTL() to i18n/direction.ts and used it to mirror the
computed position in:
- navigation-rail.tsx: storage quota popover, logout/switch-account menu
- account-switcher.tsx: both the rail and expanded-sidebar variants
- calendar-invitation-banner.tsx: the "add to calendar" picker
Adds a complete Arabic locale (2759 keys, full parity with en) and wires
it into routing, RTL direction detection, message loading, the language
switcher, and flag icons alongside the existing he/fa RTL locales.
