Added a saved Mend toggle for medics

I added MEND to the Field Medic controls. It starts on and lets an idle medic seek wounded infantry within fourteen metres, with a distinct green medical cursor for an eligible patient.

Turning Mend off stops automatic care without removing right-click healing orders. The setting survives a save, and Field Medic research now follows Bulwark. This keeps automatic support useful while leaving deliberate orders under the player's control.

“Medics can automatically seek wounded infantry nearby, with manual healing available when automatic care is off.”