Replace temporary email-based Feedback tab once server-side intake lands

[ThatXliner]

Context

We added a temporary Feedback tab to the Expo bottom tab bar that composes a mailto: to billionnewsapp@gmail.com (with app version / build / platform pre-filled) instead of submitting to the server, because server-side feedback intake isn't wired up yet.

Introduced in b1bcbf8's follow-up work — see:

• apps/expo/src/app/(tabs)/feedback.tsx (the temporary tab screen)
• apps/expo/src/app/(tabs)/_layout.tsx (registers the feedback tab)
• apps/expo/src/components/ui/TabBar.tsx (maps feedback → message icon)

Note: the existing apps/expo/src/app/settings/feedback.tsx screen already posts to trpc.feedback.submit and is hidden from the tab bar in production — left untouched.

When server-side intake lands

Do one of:

• Point the tab at tRPC — swap the mailto: submit in (tabs)/feedback.tsx for trpc.feedback.submit (mirror settings/feedback.tsx), keeping the "email us directly" fallback, or
• Remove the temporary tab — delete (tabs)/feedback.tsx, its <Tabs.Screen name="feedback" /> registration in _layout.tsx, and the feedback: "message" entry in TabBar.tsx, falling back to the existing settings/feedback form.

Point of contact

billionnewsapp@gmail.com