The US 9cm amateur allocation was cut from 3300-3500 to 3300-3450 MHz
in 2020, so 3456 (the legacy weak-signal calling frequency) is no
longer in-band. Move the canonical key to 3400, migrate existing
contacts, and keep 3456 input resolving to 3400 via the
nearest-band snap so historical ADIF/CSV logs still import cleanly.