fix(sync): fallback to historyMap on API fetch failure (#263)

[yashvi-3106]

Description

This PR resolves issue #263 where active users were being dropped entirely from the leaderboard when external API wrapper fetches failed (due to rate limiting, network timeouts, or DNS failures).

Linked Issue

Fixes #263

Changes Made

• Updated the daily fetch loop in scripts/sync-leaderboard.js to look up the user's cached records from historyMap when fetchData fails instead of logging and returning prematurely.
• Recycles the user's last known stats (easySolved, mediumSolved, hardSolved, score, etc.) if available.
• Skips the user only if no historical cached record is available.

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

Note: Tested using a mock environment by simulating API timeouts/rate-limit failures for test users and verifying that the daily sync recycled their previous overall data and scores correctly without dropping them.

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

[github-actions]

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Please ensure your changes comply with the project's contribution guidelines and that all workflow checks pass successfully.

Formatting and Branching

• Please confirm you have formatted your code locally using npx prettier --write . before requesting a review.
• Ensure this PR is made from a feature/* branch and not main.

Note: This project is currently maintained by a solo maintainer, so reviews and responses may sometimes take a little time. Thanks for your patience.

[yashvi-3106]

@jagdish-15 you can review it!

[jagdish-15]

Looks like this branch contains a few commits from your previous PR.

Could you cherry-pick just the commit related to this issue and then force-push the branch again? That'll keep this PR focused and make it easier to review.

[yashvi-3106]

@jagdish-15 you can review it now!