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.

icom_models_test.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"os"
+	"regexp"
+	"strconv"
+	"testing"
+
+	"hamlog/internal/cat/civ"
+)
+
+// The Icom model picker in the settings and civ.ModelName are two hand-kept
+// copies of the same table, and they had drifted: the UI 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 rig that simply never replies — and the backend then named it
+// as the other model.
+//
+// The list is read out of the .tsx itself, so a model added on one side alone
+// fails here rather than on someone's radio.
+func TestIcomModelAddressesMatch(t *testing.T) {
+	src, err := os.ReadFile("frontend/src/components/SettingsModal.tsx")
+	if err != nil {
+		t.Skipf("frontend source not available: %v", err)
+	}
+	re := regexp.MustCompile(`\{ name: '(IC-[A-Za-z0-9-]+)', addr: 0x([0-9A-Fa-f]{2}) \}`)
+	ms := re.FindAllStringSubmatch(string(src), -1)
+	if len(ms) < 5 {
+		t.Fatalf("only %d models found — the parse is wrong, not the data", len(ms))
+	}
+	for _, m := range ms {
+		name := m[1]
+		addr, err := strconv.ParseUint(m[2], 16, 8)
+		if err != nil {
+			t.Fatalf("bad address %q for %s", m[2], name)
+		}
+		if got := civ.ModelName(byte(addr)); got != name {
+			t.Errorf("settings offer %s at 0x%02X, but civ.ModelName(0x%02X) = %q",
+				name, addr, addr, got)
+		}
+	}
+}