- Add getServerTurnRate() accessor and turnRateOverride_ field so the
keyboard turn speed respects SMSG_FORCE_TURN_RATE_CHANGE from server
- Convert rad/s → deg/s before applying to camera yaw logic
- Fix SMSG_SPLINE_SET_RUN_BACK/SWIM/FLIGHT/FLIGHT_BACK/SWIM_BACK/WALK/
TURN_RATE handlers: all previously discarded the value; now update the
corresponding serverXxxSpeed_ / serverTurnRate_ field when GUID matches
playerGuid (camera controller syncs these every frame)