Adds sign-in support for accounts using an authenticator app (MFA). The popup now accepts a six-digit authenticator code when required and explains that extension sign-in is separate from website sign-in. Local timers and queued logs are preserved during reauthentication. No extension permissions have changed.

Simplified the volunteer-hours popup with a clean dark mode design. Added a compact timer workflow with local cycle tracking, settings in the gear menu, and full-width log submission.