perf: memoize leaderboard badge tiers

[Anthony-19]

Summary

• Memoize each leaderboard contributor’s gamification profile by contribution total.
• Add a stroop-based gamification helper without altering tier rules.
• Add a regression test proving unchanged re-renders do not recalculate badge tiers.

Verification

• npm.cmd test -- --runInBand src/__tests__/components/ContributorLeaderboard.test.tsx
• npx.cmd eslint src/components/ContributorLeaderboard.tsx src/lib/gamification.ts src/__tests__/components/ContributorLeaderboard.test.tsx
• npx.cmd prettier --check ...
• git diff --check

Notes

Project-wide TypeScript checking is currently blocked by an existing missing @web3auth/auth module dependency.

Closes #829

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[davidmaronio]

the idea is right: calculateGamificationProfileFromStroops is a sensible helper that keeps tier rules in one place, and memoizing per-contributor profiles in the leaderboard plus a regression test that unchanged re-renders do not recalculate is exactly what #829 asked for.

but the PR cannot be merged in its current shape:

1. the diff touches 30+ files that have nothing to do with the leaderboard (jest.config.ts, playwright.config.ts, i18n scripts, WalletContext, DonationContext, many unrelated tests, .vscode/settings.json) and github reports the branch as conflicting. it looks like the branch was cut from the broken pre-#875 main. please rebase onto current main and reduce the diff to ContributorLeaderboard.tsx, gamification.ts, and the new test.
2. src/lib/gamification.ts: most of the file's hunks are quote-style reformatting (single to double quotes). formatting churn belongs to prettier on main, not this PR; after the rebase these hunks should disappear or be dropped.
3. .vscode/settings.json should not be added to the repo in a perf PR; please remove it.
4. src/lib/gamification.ts (calculateGamificationProfileFromStroops): Number(totalAmountStroops) loses precision above 2^53 stroops. unlikely in practice but a one-line comment or a clamp would document the assumption.