Improve tiebreak when tracks have same score

[mintopia]

The users are on to us. We need to fix the ordering when tracks are tied.

Currently it breaks ties on the created_at timestamp for the request, instead it should probably be ascending order of when it achieved that score - so the oldest one that reached the current score should be picked.

To do this, we need to store the last score changed timestamp and use that as the ordering criteria.

Finally if that doesn't break the tie, order by user ID ASC, so the party admin gets picked as we have the lowest ID.

[VibroAxe]

this is similar to what i was looking at here>

#45 (comment)