TPG.Maps.GetSafezoneRadius

The current map's spawn-protection radius. Every map block below authors safezoneRadius, and until this existed nothing read it -- all four consumers went straight to TPG.Config.safezoneRadius, so the per-map value was a knob that turned nothing. Every authored value happens to equal the global default, so wiring it up changes no map's behaviour today; it just means editing one starts working.