feat: IC-7300MKII, and two Icom addresses that were plain wrong

Adds the IC-7300MKII at CI-V 0xB6.

Doing so exposed a drift between the two hand-kept copies of the model table: the
settings offered the IC-7700 at 0x88 and the IC-7800 at 0x80, which are the
IC-7100's and the IC-7410's factory addresses. Picking either set an address the
rig never answers on — the symptom is a radio that simply stays silent — and the
backend then named it as the other model. Corrected to 0x74 and 0x6A, and the
four models the backend already knew (IC-7100, IC-7410, IC-7600, IC-7851) are now
offered too instead of forcing a manual address.

A test reads the model list out of the .tsx and asserts civ.ModelName agrees, so
the next model added on one side alone fails the build rather than someone's
radio.

internal/cat/civ/civ_test.go

@@ -152,6 +152,7 @@ func TestModelNameAddresses(t *testing.T) {
 		0x98: "IC-7610",
 		0xA2: "IC-9700",
 		0xA4: "IC-705",
+		0xB6: "IC-7300MKII",
 	} {
 		if got := ModelName(addr); got != want {
 			t.Errorf("ModelName(0x%02X) = %q, want %q", addr, got, want)