fix(logging): say why the antenna stopped and what the ADIF port is receiving

Two problems from one operator's log, both of them the log's fault.

SteppIR. The last line about it is "status query failed, reconnecting: Port
has been closed" and then nothing — for the rest of the session. The poll loop
does retry every two seconds, but a failed open was a bare `continue`: no line,
ever. And startUltrabeam had three silent ways out — settings unreadable, the
antenna turned off, no port or host configured — so a cleared field and a lost
adapter produced exactly the same evidence, which is none. Both now say what
happened, with the port or host named. Reopen failures are reported three
times and then throttled (a port that is gone stays gone), and the recovery
says how many attempts it took.

FLDIGI. Four hundred "ADIF payload ignored" lines and nothing else legible.
The cause is in the same log: two inbound listeners on the SAME multicast
group and port, 239.255.0.1:2237 — one WSJT (MSHV), one ADIF (FLDIGI). Every
WSJT-X packet is delivered to both, and an FT8 cycle is dozens of decodes
every fifteen seconds; the bursts in the log are exactly 15 s apart. The ADIF
listener now checks for the WSJT-X magic and says so once, with what to do
about it, instead of rejecting each packet in writing. Anything else is
described a few times with its payload and then goes quiet.

internal/integrations/udp/adifignore_test.go

@@ -0,0 +1,40 @@
+package udp
+
+import (
+	"encoding/binary"
+	"testing"
+)
+
+// An operator's log arrived with four hundred identical "ADIF payload ignored"
+// lines and nothing else legible: two inbound listeners were configured on the
+// SAME multicast group and port, one WSJT and one ADIF, so every WSJT-X decode
+// was delivered to both and the ADIF one rejected each in writing. An FT8 cycle
+// is dozens of decodes every fifteen seconds.
+//
+// The listener has to recognise that traffic and say what it is — once.
+func TestIgnoredADIFStaysBounded(t *testing.T) {
+	s := &Server{cfg: Config{Name: "FLDIGI", Port: 2237}}
+
+	// A WSJT-X packet: magic first. One line is the whole diagnosis, so the
+	// counter is pushed past the cap immediately.
+	pkt := make([]byte, 16)
+	binary.BigEndian.PutUint32(pkt[:4], wsjtMagic)
+	s.noteIgnoredADIF(pkt)
+	if s.badPkts <= maxBadPktDumps {
+		t.Errorf("badPkts = %d — WSJT traffic should silence the listener at once", s.badPkts)
+	}
+
+	// Anything else is described a few times before going quiet, so an ordinary
+	// keep-alive does not get the same one-line treatment as a real diagnosis.
+	s2 := &Server{cfg: Config{Name: "FLDIGI", Port: 2237}}
+	s2.noteIgnoredADIF([]byte("keep-alive"))
+	if s2.badPkts > maxBadPktDumps {
+		t.Errorf("one unusable payload silenced the listener (badPkts = %d)", s2.badPkts)
+	}
+	for i := 0; i < 50; i++ {
+		s2.noteIgnoredADIF([]byte("keep-alive"))
+	}
+	if s2.badPkts <= maxBadPktDumps {
+		t.Errorf("badPkts = %d — the throttle never engaged", s2.badPkts)
+	}
+}