fix: clamp period deltas at 0 in processTimeframe to prevent negative…

[Tamcodes4]

Description

This PR fixes an issue where the daily, weekly, and monthly leaderboards could display negative solved counts and negative scores when a user's cumulative totals temporarily decreased (for example, due to an inconsistent API response).

processTimeframe() in scripts/sync-leaderboard.js previously calculated period deltas using direct subtraction, which could produce negative values. This change clamps the solved counts to a minimum of 0 using Math.max(0, ...) before recalculating the derived score and totalSolved values.

Linked Issue

Fixes #238

Changes Made

• Replaced direct subtraction with Math.max(0, current - previous) for:

  • easySolved
  • mediumSolved
  • hardSolved

• Left the existing score and totalSolved calculations unchanged so they automatically derive from the clamped values.

• Preserved the existing calculation flow while preventing invalid negative values from propagating to 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

Manual Verification

Verified the logic using a scenario where a user's previous cumulative snapshot exceeded the current snapshot. Confirmed that:

• easySolved, mediumSolved, and hardSolved are clamped to 0 instead of becoming negative.
• score is recalculated from the clamped values and never becomes negative.
• totalSolved is derived from the corrected solved counts and remains non-negative.

No automated tests were added since this repository does not currently include a test suite for the leaderboard sync scripts.

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

N/A – Backend data-processing change only. No UI or visual changes.

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