Move to Go 1.27, and fix initials for non-ASCII names

Initials() capped the loop with len(out) == 2, which counts bytes: a name
starting with Ä, Ö or Å filled the budget on its own and returned a single
letter. Count the initials taken instead.

go fix also wanted a strings.Builder here, but that allocates a string per
iteration to measure a two-character result. Took its SplitSeq suggestion
in lyrics.go, which drops an intermediate slice.

auth.go

@@ -35,10 +35,11 @@ type member struct {
 
 // Initials for the avatar circle: no default image on disk, no identicon generator.
 func (m *member) Initials() string {
-	out := ""
+	out, n := "", 0
 	for _, f := range strings.Fields(m.Name) {
 		out += strings.ToUpper(string([]rune(f)[0]))
-		if len(out) == 2 {
+		// ponytail: count runes taken, not bytes — "Ä" is 2 bytes and used to end the loop early.
+		if n++; n == 2 {
 			break
 		}
 	}