fix: leaderboard out of sync url state

[djbarnwal]

The URL state allows two independent parameters that should be dependent.

The bug is a state synchronization issue:

• URL allows inconsistent state: sort_by and leaderboard_measures can diverge
• Data fetching uses sort_by for sorting but UI displays leaderboard_measures

Modified the setLeaderboardSortByMeasureName action to automatically keep leaderboard_measures in sync with sort_by

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!