feat(bandmap): mark LoTW users, with the badge the cluster already uses

Logger32 draws a green square for a LoTW user and an X for a worked one. The
square is the part worth copying; the way it is drawn is not.

Colour on this map is already spoken for — it carries the entity status, and
the left edge of each pill stacks the new-park / new-county markers. Adding a
green fill for LoTW would put two unrelated meanings on one channel, and an
operator would have to work out which green meant what. So it is the same "L"
badge the cluster list draws, in the same muted blue, for the reason written
there: whether a station uploads to LoTW says nothing about whether the spot is
worth chasing.

Worked stations already read as worked here — the pill goes grey and the
status markers speak — so no X is needed.

Switchable in Settings → Appearance, and on by default: a `configured` flag
distinguishes "saved with this off" from "saved before the option existed", so
turning it off sticks instead of being undone by the next default.

appearance.go

@@ -33,8 +33,16 @@ type RowColorSettings struct {
 	// behind it. The stripe says the same thing and costs nothing to read.
 	Style string `json:"style"`
 	// Intensity is the tint strength in percent. Only used by "tint"/"both".
-	Intensity int            `json:"intensity"`
-	Rules     []RowColorRule `json:"rules"`
+	Intensity int `json:"intensity"`
+	// BandMapLotw marks stations that upload to LoTW on the band map, with the
+	// same "L" badge the cluster list uses — one visual vocabulary across the two
+	// views rather than a second invention.
+	BandMapLotw bool `json:"bandmap_lotw"`
+	// Configured distinguishes "saved with this off" from "saved before the
+	// option existed", so a new marker can default ON without silently turning
+	// itself back on for an operator who switched it off.
+	Configured bool           `json:"configured"`
+	Rules      []RowColorRule `json:"rules"`
 }
 
 // The rule ids, in priority order. The frontend matches on these and holds the
@@ -66,7 +74,13 @@ func normRowColors(s RowColorSettings) RowColorSettings {
 	for _, r := range s.Rules {
 		byID[r.ID] = r
 	}
-	out := RowColorSettings{Enabled: s.Enabled, Style: s.Style, Intensity: s.Intensity}
+	out := RowColorSettings{
+		Enabled: s.Enabled, Style: s.Style, Intensity: s.Intensity,
+		BandMapLotw: s.BandMapLotw, Configured: true,
+	}
+	if !s.Configured {
+		out.BandMapLotw = true // new option, on unless the operator says otherwise
+	}
 	switch out.Style {
 	case "bar", "tint", "both":
 	default: