- Fix bug: biggestCountrySize used club instead of country
- Add local club detection (>40% threshold)
- When local club exists (non-legacy mode):
* Local club members paired together: get FULL different-club bonus
* Ist vs non-Ist (different clubs): normal bonus
* Strangers from same visiting club: no bonus (normal same-club)
- Legacy mode unchanged for test compatibility
- Add LocalClubTest for local club behavior verification
