feat(hamlog): mark an already-uploaded log through bulk edit

A log sent to hamlog.online by hand — an ADIF exported from OpsLog and dropped
on their site — had no way of being marked as sent afterwards. The QSL Manager
then listed every one of those contacts as backlog and offered to upload them a
second time.

Both HAMLOG keys join the bulk-editable extras, so a selection (or the whole
log) can be stamped in one pass. They are DATES rather than Y/N flags because
that is the shape the sent stamp already uses: the QSL Manager's backlog asks
whether the key is present, and a date also says when it went.

The test pins that they are reachable through the extras path and NOT offered as
columns — a mapping claiming both would write to a table that has neither.

internal/qso/bulkmode_test.go

@@ -24,3 +24,25 @@ func TestBandIsNotBulkEditableAlone(t *testing.T) {
 		}
 	}
 }
+
+// A log uploaded to HAMLOG.online BY HAND has to be markable afterwards, or
+// OpsLog offers to send every one of those contacts again. Both directions live
+// in extras — the ADIF names a field for hamlog.EU and none for hamlog.ONLINE —
+// so they must be reachable through the extras path, not the column one.
+func TestHamlogFieldsAreBulkEditable(t *testing.T) {
+	for field, want := range map[string]string{
+		"hamlog_sent": "APP_OPSLOG_HAMLOG_SENT",
+		"hamlog_rcvd": "APP_OPSLOG_HAMLOG_QSL",
+	} {
+		if got := BulkExtraKey(field); got != want {
+			t.Errorf("BulkExtraKey(%q) = %q, want %q", field, got, want)
+		}
+	}
+	// And they are NOT columns: a mapping that also claimed a column would write
+	// to a table that has none.
+	for _, col := range []string{"hamlog_sent", "hamlog_rcvd", "APP_OPSLOG_HAMLOG_SENT"} {
+		if BulkEditable(col) {
+			t.Errorf("%q is offered as a bulk-editable COLUMN", col)
+		}
+	}
+}