fix(qsl): separate the QSL manager from the routing method (#16)

QSL_VIA is the manager. QSL_SENT_VIA and QSL_RCVD_VIA are the ADIF "QSL Via"
enumeration — B bureau, D direct, E electronic, M manager (import-only) —
and say how a card travelled. OpsLog had one column for all three:

  - the import folded QSL_SENT_VIA into QSL_VIA whenever QSL_VIA was empty,
    which is exactly a Log4OM export (it defaults QSL_SENT_VIA to E), so
    OE6CLD saw "E" everywhere OpsLog shows the manager;
  - QSL_RCVD_VIA was listed in adifPromoted with no column behind it, so it
    was not stored, not kept among the extras, and not exported — dropped
    outright on import;
  - neither was ever written on export, so an import followed by an export
    destroyed both;
  - and OpsLog polluted the field itself: the QSL Manager panel wrote
    "Bureau" / "Direct" / "Electronic", in full words, into QSL_VIA.

Two columns added (migration 0027), carried through the five places a
promoted ADIF field has to touch, with round-trip tests pinning the reported
case. The QSL panel now offers Bureau / Direct / Electronic for each
direction and stores the enumeration; the manager field is labelled as the
manager and holds only that. M is kept when a file gives it and never
written back out.

Existing logs hold a mixture of the two in one column. The repair is offered,
not performed: the count is shown once per log with a plain question, and a
"no" is remembered. It moves only where QSL_SENT_VIA is still empty, and only
values that normalise to the enumeration — a manager is a callsign and can
never be one of those six words, which a test pins against real manager calls.

internal/adif/qslvia_test.go

@@ -0,0 +1,37 @@
+package adif
+
+import "testing"
+
+func TestNormaliseQSLVia(t *testing.T) {
+	for in, want := range map[string]string{
+		"B": "B", "b": "B", "Bureau": "B", "BUREAU": "B", " buro ": "B",
+		"D": "D", "Direct": "D", "direct": "D",
+		"E": "E", "Electronic": "E", "électronique": "E", "OQRS": "E",
+		"M": "M", "Manager": "M",
+		// A manager's callsign is not a routing method, and neither is noise.
+		"M0OXO": "", "EA5GL": "", "": "", "Bureau via M0OXO": "", "X": "",
+	} {
+		if got := NormaliseQSLVia(in); got != want {
+			t.Errorf("NormaliseQSLVia(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+// The repair moves values out of the manager column. A false positive would
+// erase a real manager, so the guard is worth its own test: every callsign-like
+// value must be refused.
+func TestIsQSLViaRoutingRefusesManagers(t *testing.T) {
+	for _, call := range []string{
+		"M0OXO", "EA5GL", "F5CWU", "DJ9ZB", "W3HNK", "IK2DUW", "N7RO",
+		"BUREAU M0OXO", "via bureau DL1XYZ", "QSL DIRECT ONLY",
+	} {
+		if IsQSLViaRouting(call) {
+			t.Errorf("%q was taken for a routing method — the repair would erase it", call)
+		}
+	}
+	for _, v := range []string{"B", "D", "E", "M", "Bureau", "Direct", "Electronic"} {
+		if !IsQSLViaRouting(v) {
+			t.Errorf("%q should be recognised as a routing method", v)
+		}
+	}
+}