Choose CICS or IMS backend per application

Each application now declares its remote screen backend—CICS over MQ or IMS Connect—at creation time. That choice is immutable and gates which map types you can import, so CICS BMS and IMS MFS descriptors stay aligned with the host transport.

Map descriptors, samples, and Player sessions are scoped per operation within the application. UI polish includes green-screen previews during mainframe member selection and clearer import chooser flows.