[ENHANCEMENT] Bottom Navigation Bar

[blu3eee]

User Story
As a user, I want to switch between professor search, course search, and settings easily in the Chrome extension to improve my experience.

Technical Tasks

• Design and implement a bottom navigation bar with three tabs: Professor Search, Course Search, and Settings.
• Test navigation for usability and accessibility.

Acceptance Criteria

• Bottom navigation is always visible and accessible.
• Users can switch between tabs.