Notifications were silently dropped when the app was in the foreground
on a different tab: BackgroundService short-circuited on
isAppInBackground() and there was no foreground path. Add a system
notification dispatch in useConnectionLifecycle that fires when the
message lands in a tab other than the active one, gated on
!backgroundService.isAppInBackground() to avoid duplicates.

NotificationService.shouldNotify never consulted highlightService, so
custom highlight words only affected UI rendering, not alerts. Check
highlightService.isHighlighted() inside the notifyOnMentions branch and
extend the MENTION sound path to fire on highlight matches too.

Bump app to 1.9.34 / versionCode 139 and refresh dependencies:
Firebase 24.1.1->25.1.0, RN community CLI 20.1.3->20.2.0, Reanimated
4.4.1->4.5.0, Worklets 0.9.2->0.10.0, plus patch releases for
Transifex, bootsplash, IAP, keyboard-controller, nitro-modules,
google-mobile-ads, testing-library, @types/node and prettier.