feat(hamqth): QSO upload to the HamQTH logbook — the 8th external service

qso_realtime.php with the account's callbook credentials (which the
external-services config falls back to when its own are blank), one ADIF
record per QSO, prg=OpsLog. HTTP status IS the answer: 200 saved, 400
rejected (a duplicate counts as delivered, like HRDLog's insert 0), 403
credentials. Sent-state lives in APP_OPSLOG_HAMQTH_SENT extras like
HAMLOG.online — ADIF names no HamQTH field. Auto-upload on log, on-close
batch, right-click Send to, QSL Manager backlog, and a Test button that
authenticates against the callbook login, which cannot touch the log.

Fixes a real mis-route on the way: manual 'Send to HAMLOG.online' had no
branch in runManualUpload and fell through to QRZ.com — the selection was
uploaded to the wrong service with the QRZ key. Both extras-stamped
services now have their own branch.

internal/extsvc/extsvc.go

@@ -38,6 +38,9 @@ const (
 	ServiceCloudlog Service = "cloudlog"
 	// ServiceHamlog is HAMLOG.online — one API key, an ADIF record per QSO.
 	ServiceHamlog Service = "hamlog"
+	// ServiceHamQTH is the HamQTH online logbook — the callbook credentials,
+	// one ADIF record per QSO.
+	ServiceHamQTH Service = "hamqth"
 )
 
 // UploadMode selects when an auto-upload fires after a QSO is saved.
@@ -133,6 +136,7 @@ type ExternalServices struct {
 	EQSL     ServiceConfig `json:"eqsl"`
 	Cloudlog ServiceConfig `json:"cloudlog"`
 	Hamlog   ServiceConfig `json:"hamlog"`
+	HamQTH   ServiceConfig `json:"hamqth"`
 
 	// 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