perf: paginate inactive users on leaderboard to prevent layout freeze (#299)

[yashvi-3106]

Description

Resolves a performance freeze/lag when navigating to the last page of the leaderboard. This occurred because all inactive users (those with an overall score of 0) were loaded and appended to the table at the same time on the last page. Paginating inactive users incrementally within the unified leaderboard array avoids this rendering lockup.

Linked Issue

Fixes #299

Changes Made

• Combined active users (overall score > 0) and inactive users (overall score 0) into a single unified leaderboard array (combinedData) in applyFiltersAndRender().
• Calculated all pagination attributes (totalPages, startRow, endRow) and stats based on the unified array length.
• Updated renderLeaderboard() to slice the combined array per page and dynamically insert the ── [ SECTION: NO ACTIVITY YET ] ── divider row/card before the first inactive user.
• Correctly computed active user ranks based on their active list index (or originalRank) and set inactive user ranks to "".

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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