[WIP] Merge LTS to latest code version

[Copilot]

• Fix addXP validation to allow xp=0
• Fix leaderboard performance by using Promise.all for member fetching
• Fix connect.js to propagate auto_purge option
• Fix rank.js ctx.restore() without matching ctx.save()
• Fix eslint.config.cjs sourceType to "script" for CommonJS
• Fix addLevel validation to allow level=0
• Update error messages to be consistent and accurate
• Use consistent NaN checking (Number.isNaN) across files
• Optimize leaderboard deletion with batch deleteMany operation

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[codacy-production]

Codacy's Analysis Summary

0 new issue (≤ 0 medium issue)
0 new security issue (≤ 0 issue)

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