Fix contest highlight bug when page changes

[AdityaBVerma]

Fix: Friend highlight persists across contest ranking pages (#48)

What was happening

When switching pages in the contest rankings, friend highlights sometimes carried over to the next or previous page.
This happened because LeetCode reuses table rows and the previously applied inline styles were never cleared.

What I changed

I added a small cleanup step before applying highlights:

• A new clearHighlights() function removes any existing highlight styles
• It runs at the start of action() so each page starts fresh

Result

• Highlights now appear only on pages where the friend is actually present
• Moving back and forth between pages no longer leaves stale highlights

Screen.Recording.2026-01-14.170046.mp4

Fixes #48