fix(tci): subscribe to the radio's meters; fix the new-spot count; explain an SMTP refusal

TCI meters: the S-meter came only from RX_SMETER and the transmit meters from
TX_POWER / TX_SWR — commands ExpertSDR3 does not send. The protocol's answer is
a subscription (RX_SENSORS_ENABLE / TX_SENSORS_ENABLE, §4.4 of the TCI PDF),
after which the radio pushes RX_CHANNEL_SENSORS and TX_SENSORS. Nobody had
asked, so the console's meters sat empty in RX and in TX while everything else
worked.

Cluster: the held-spot counter looked for the row it froze on. A station spotted
again REPLACES its row, so that row vanishes in the ordinary course of things
and the count fell through to 'everything is new' — 4, 5, then 500. Counted by
timestamp now, which survives both the replacement and the ring buffer.

SMTP: '535 5.7.139 basic authentication is disabled' is a policy, not a typo.
The message now says so, and says what actually helps, without claiming a policy
when the server simply rejected the password.

internal/cat/tci.go

@@ -155,6 +155,13 @@ func (t *TCI) Connect() error {
 	t.mu.Unlock()
 	debugLog.Printf("TCI: connected to %s", url)
 	go t.reader(conn)
+	// Ask for the meters. Nothing measures anything until this goes out: the
+	// S-meter, the transmit power and the SWR are all pushed by the radio, and
+	// only to a client that has subscribed. 200 ms is the rate the protocol's own
+	// examples use — fast enough for a needle, slow enough not to flood a socket
+	// that also carries audio.
+	_ = t.send("rx_sensors_enable:true,200;")
+	_ = t.send("tx_sensors_enable:true,200;")
 	if t.spotsEnabled {
 		// Forget what we thought was on the panorama at the same moment the radio
 		// is told to drop it. Kept, the memory would suppress the next spot for