Return stable public counts for the games catalog filters.

The catalog's visible match list is filter-specific and paginated, so
deriving badge counts from that list makes every other tab collapse to
zero after a filter click. Keep those counters server-derived instead.

GET /api/v1/games/matches/summary/?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "counts": {
        "all": 0,
        "live": 0,
        "finished": 0,
        "mafia": 0,
        "liars_dice": 0,
        "monopoly": 0,
        "las_vegas": 0,
        "diplomacy": 0
    },
    "live_game_types": []
}