feat: HAMLOG.online upload and confirmations, Yaesu antenna, a named port holder

HAMLOG.online is a seventh external service: one API key, one ADIF record per
QSO, immediate / delayed / on-close like the rest. They publish no API
documentation, so the protocol is read from THEIR OWN client — the HAMLOG Agent
(github.com/hamlogonline/Agent), which is the authoritative source short of
asking them:

	POST https://hamlog.online/api/agent/
	{"ADIFADD": {"APIKEY": k, "ADIFDATA": record}}   → {"STATUS":"OK"}
	{"KEYSTATUS": {"APIKEY": k}}                     → {"STATUS":"OK","CALLSIGN":…}

Success is STATUS == OK, not "no ERROR field": their failure carries ERROR and
no STATUS, and reading an unknown reply — a proxy page, a maintenance notice —
as an acceptance is how a contact goes missing without anyone noticing.

KEYSTATUS buys something no other service here offers: the key can be checked
BEFORE the first QSO, and the answer names the account. A key pasted from
another callsign is caught in the settings panel rather than through a week of
silent refusals.

Their confirmations are also an award source now, ticked like LoTW rather than
expressed through "custom". It reads the ADIF extras, not a column: the standard
names a field for hamlog.EU and none for hamlog.ONLINE, and borrowing the other
site's field would write a falsehood into every exported log. Three plausible
key names from their own export are accepted too, so nobody has to rename a
column by hand after an export.

Yaesu gains antenna selection (AN), remembered per band — the antenna picked on
a band comes back with it, with no table to fill in anywhere. Rigs with one
socket never answer AN and never show the row; the log says which case it is.

And a serial port that is refused now names its likely holder. OmniRig stays
resident once activated and keeps the port of the rig configured in it, so a
native backend never gets it — "Serial port busy" alone accused nobody, and an
FTDX10 spent a morning being blamed for it.

internal/extsvc/extsvc.go

@@ -36,6 +36,8 @@ const (
 	// ServiceCloudlog covers Cloudlog AND its fork Wavelog: same API contract,
 	// only the instance URL differs, so one service handles both.
 	ServiceCloudlog Service = "cloudlog"
+	// ServiceHamlog is HAMLOG.online — one API key, an ADIF record per QSO.
+	ServiceHamlog Service = "hamlog"
 )
 
 // UploadMode selects when an auto-upload fires after a QSO is saved.
@@ -130,6 +132,7 @@ type ExternalServices struct {
 	HRDLog   ServiceConfig `json:"hrdlog"`
 	EQSL     ServiceConfig `json:"eqsl"`
 	Cloudlog ServiceConfig `json:"cloudlog"`
+	Hamlog   ServiceConfig `json:"hamlog"`
 
 	// DeleteRemote asks OpsLog to withdraw a QSO from QRZ.com and Club Log when
 	// it is deleted locally. Off unless the operator turns it on: neither