feat(lookup): optional QRZ nickname as the logged name

QRZ publishes <nickname> — the name an operator goes BY on the air — and
OpsLog was composing fname + name instead. "Bob" is what belongs in a log;
"Robert J Smith" is what belongs on a licence.

QRZ only, and deliberately so: HamQTH's <nick> already fills the Name field
that way, so the same switch there would toggle a behaviour it has no way to
turn off.

A published nickname is optional, so an empty one falls through to the
registered name. That is the whole point of it being a fallback rather than a
swap, and it is what the test pins — a blank nickname must never blank the
name.

internal/lookup/qrzname_test.go

@@ -0,0 +1,31 @@
+package lookup
+
+import "testing"
+
+// The nickname is the name an operator goes BY on the air, and that is what
+// belongs in a log — "Bob", not "Robert J Smith". HamQTH's <nick> is already
+// used that way; this brings QRZ into line for operators who ask for it.
+//
+// The one thing it must never do is blank the name. A published nickname is
+// optional, so an empty one has to fall through to the registered name rather
+// than win by being "preferred".
+func TestQRZNamePrefersNicknameButFallsBack(t *testing.T) {
+	for _, tc := range []struct {
+		prefer                bool
+		nickname, fname, name string
+		want                  string
+	}{
+		{true, "Bob", "Robert", "Smith", "Bob"},
+		{true, "", "Robert", "Smith", "Robert Smith"},     // no nickname published
+		{true, "   ", "Robert", "Smith", "Robert Smith"},  // blank is not a nickname
+		{false, "Bob", "Robert", "Smith", "Robert Smith"}, // option off
+		{true, "Bob", "", "", "Bob"},
+		{false, "", "Robert", "", "Robert"},
+		{true, "", "", "Smith", "Smith"},
+	} {
+		if got := qrzName(tc.prefer, tc.nickname, tc.fname, tc.name); got != tc.want {
+			t.Errorf("qrzName(%v, %q, %q, %q) = %q, want %q",
+				tc.prefer, tc.nickname, tc.fname, tc.name, got, tc.want)
+		}
+	}
+}