feat(appearance): give the worked-with-this-call dot its own two colours

The dot is drawn over all five cell backgrounds, so it cannot borrow one of
their colours; it defaults to the theme foreground with a background ring and
now takes two overrides of its own, worked and confirmed, alongside the rest of
the matrix palette.

appearance.go

@@ -174,6 +174,11 @@ type MatrixColors struct {
 	EntityWorked    string `json:"entity_worked"`
 	NotWorked       string `json:"not_worked"`
 	CurrentEntry    string `json:"current_entry"`
+	// The dot marking a slot already worked with the callsign in hand. It is a
+	// mark rather than a background, so it needs its own two colours: it is
+	// drawn on top of all five of the above and must stay legible over each.
+	MarkWorked    string `json:"mark_worked"`
+	MarkConfirmed string `json:"mark_confirmed"`
 }
 
 // normMatrixColors keeps only plain hex values. Anything else becomes "" — i.e.
@@ -196,6 +201,8 @@ func normMatrixColors(c MatrixColors) MatrixColors {
 		EntityWorked:    clean(c.EntityWorked),
 		NotWorked:       clean(c.NotWorked),
 		CurrentEntry:    clean(c.CurrentEntry),
+		MarkWorked:      clean(c.MarkWorked),
+		MarkConfirmed:   clean(c.MarkConfirmed),
 	}
 }