v0.260.0 — a box ahead of the catalog reads „Naprakész", and the pin never moves backwards (R-524)

MEASURED 2026-09-15 (BIGNIGHT Phase 6): privatebin updated 2.0.5 -> 2.0.6, catalog
reverted to 2.0.5, and the box read „Frissítés elérhető — ma" over an Update that
would have moved the pin BACKWARDS onto a possibly-migrated datadir.

- stacks.CatalogOrder: the comparison gains a fourth answer (Ahead) and moves out of
  web, so the badge and UpdatePreflight cannot drift apart.
- The badge: ahead reads „Naprakész"/"Up to date", tag-ok, with a title saying why.
- The refusal: UpdatePreflight returns `downgrade` (409), born as a bundle key; the
  API now renders update refusals through errText so it reaches English households.
- Ahead is narrow: every differing service must be orderable AND newer, else Behind.
- Ordering is util.Version.Compare behind a tag normaliser — no second comparator.
- Three red-proofs, each seen to fail.

R-589 was already fixed in v0.258.0; only its register row was stale.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/web/i18n_web.go

@@ -374,6 +374,13 @@ func (s *Server) localeFuncs(lang string) template.FuncMap {
 					Class: "tag-ok",
 					Title: b.Msg(lang, "badge.update.current.title"),
 				}
+			case updateAhead:
+				// R-524's twin. Same word, same class as updateCurrent — see updatebadge.go.
+				return &MetaBadge{
+					Label: b.Msg(lang, "badge.update.current"),
+					Class: "tag-ok",
+					Title: b.Msg(lang, "badge.update.ahead.title"),
+				}
 			case updateBehind:
 				label := b.Msg(lang, "badge.update.behind")
 				if days, ok := st.Meta.CatalogSinceAge(time.Now().UTC()); ok {