fix: prevent rank change tooltip from overlapping sticky leaderboard header

[shineetejol9]

Description

This PR fixes the rank change tooltip being partially hidden behind the sticky leaderboard header on narrower screen widths.

The tooltip position is adjusted for the affected top leaderboard rows, ensuring it remains fully visible while preserving the existing behavior for the remaining rows.

Linked Issue

Fixes #266

Changes Made

• Prevented rank change tooltips from overlapping the sticky leaderboard header.
• Adjusted tooltip positioning for the affected leaderboard rows.
• Preserved the existing tooltip behavior for the rest of the leaderboard.

Type of Change

• Bug fix
• New feature
• UI/Visual update
• Documentation update
• Refactor

Testing

• Tested locally
• Tested on mobile viewport (if applicable)
• No console errors introduced

Checklist

• My code follows the project's coding style
• I have formatted my code locally by running npx prettier --write . before submitting
• I am submitting my PR from a dedicated feature/* branch, not the main branch
• I have performed a self-review of my code
• My changes generate no new warnings or errors
• I have updated documentation if required
• I have linked the relevant issue

Screenshots / Screen Recording

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