fix: links/client side navigation

[js0mmer]

Description

Some anchor tags were used to link to other pages. Link tags need to be used instead to use react router properly for client side navigation. Also had to fix some useEffect dependencies and keys in some components because data was persisting between changing courses, professors, etc. now that we're actually navigating on the client and not reloading the page.

Next Steps

• We should fix the remaining lint warnings for missing useEffect dependencies
• Should also fix all the keys that aren't unique to the data being shown in the component (Fix react key attributes to be unique #314)

I think I took care of everything to make navigation work properly but we should do the above steps to be sure and to avoid any inevitable errors that may occur in the future.

Steps to verify/test this change:

• Verify changes work as expected on staging instance

Final Checks:

• Verify successful deployment

(optional)

• Write tests
• Write documentation

Issues

Closes #