Title: Add property test for leaderboard metric calculation accuracy

[Emmyt24]

Description
Implement a property test proving leaderboard metrics (burn amounts, counts) are calculated accurately.

Requirements and context

• Must be secure, tested, and documented where applicable
• Should stay reviewable and fit the current monorepo structure

Suggested execution

• Create branch: add-property-test-for-leaderboard-metric-accuracy
• Keep changes scoped to the issue and reference the task IDs in the PR

Implement changes

• Generate random burn records for tokens
• Run at least 100 iterations and annotate Property 79
• Assert aggregated amounts match sum of individual burns
• Verify counts match number of burn records

Test and commit

• Run the most relevant tests for the touched service or UI surface
• Include metric calculation examples
• Call out edge cases, assumptions, and any follow-up work

Example commit message

test: add leaderboard metric accuracy property

Guidelines

• Prefer small, reviewable PRs
• Keep naming and data contracts consistent with the spec docs
• Preserve responsive and accessible behavior for frontend work

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