fix: /B was not recognized in the cluster

internal/dxcc/dxcc.go

@@ -303,11 +303,12 @@ func normalizeCallsign(s string) string {
 		if p == "" {
 			continue
 		}
-		// A TRAILING /MM (maritime) or /AM (aeronautical) mobile is stripped and
-		// the operator's home entity is kept, so the contact still resolves to a
-		// country in the log (e.g. YB1SCY/AM → Indonesia). A LEADING "MM" is the
-		// Scotland operating prefix (MM/F4NIE) and must NOT be stripped.
-		if i > 0 && (p == "MM" || p == "AM") {
+		// A TRAILING /MM (maritime) or /AM (aeronautical) mobile, or /B (beacon), is
+		// stripped and the operator's home entity is kept, so the contact still
+		// resolves to a country in the log (e.g. YB1SCY/AM → Indonesia, 4U1UN/B →
+		// 4U1UN → United Nations HQ). A LEADING "MM"/"B" is a PREFIX (MM = Scotland,
+		// B = China: B/F4NIE) and must NOT be stripped.
+		if i > 0 && (p == "MM" || p == "AM" || p == "B") {
 			continue
 		}
 		if suffixModifiers[p] {

internal/dxcc/dxcc_test.go

@@ -224,6 +224,8 @@ func TestNormalize(t *testing.T) {
 		"MM/LY3X/P":  "MM",
 		"F4BPO/W6":   "W6",
 		"VK9/F4BPO":  "VK9",
+		"4U1UN/B":    "4U1UN", // trailing /B = beacon → strip, keep the base call
+		"B/F4BPO":    "B",     // leading B = China operating prefix, NOT a beacon
 	}
 	for in, want := range cases {
 		if got := normalizeCallsign(in); got != want {