Allow restoring hidden translate bar

[redactdeveloper]

Summary

• keep the peer menu restore action available whenever translations are hidden for that peer
• remove the dependency on a loaded history, detected source language, or current translated state
• use the existing "Show Translate Button" label for the restore action

This makes the hide action reversible from the peer menu and addresses #291.

Fixes #291.

Verification

• Ran git diff --check
• Full AyuGram Desktop build was not run locally because this checkout does not include the full dependency/build environment.