Tournaments are now fair

Fixed a serious bug in Arena tournaments that was quietly corrupting ratings. In short: when both players in a match clicked “I won” at the same time, the game sometimes counted the result twice. One player got double the rating change up, the other double down. The bracket occasionally got skewed.

This cannot happen now: only the first click changes anything, the second is politely ignored. We checked all similar places in tournament code — found three more (double XP for top 3, duplicate matches in the next round, biased pairings) and fixed those too.

If in past tournaments you had a strange rating jump — that was it. We are not retroactively fixing the numbers (too risky for the database), but from now on everything counts cleanly.

The first round draw also became truly random — there used to be a slight bias in pairings.