Average all wake force struct fields

[ronangiss]

Summary

• Change phase_avg_STB to store lift_phase_avg and drag_phase_avg as structs.
• Initialize phase-average arrays from all fields returned by get_wake_lift.
• Average each returned lift/drag field per phase bin instead of only lift.vortX and drag.tot.

Testing

• git show --check --stat --oneline HEAD
• Static wake force averaging check for phase_avg_STB.m
• MATLAB block-balance check for phase_avg_STB.m

Notes

• MATLAB/Octave is not installed in this cloud environment, so runtime execution is limited to static validation here.