Part E: the stale zero-toggle line tells the truth (v0.126.0)

- offboxWarningDisplay(lastWarning, toggledCount) — pure DISPLAY pick, no state mutation:
  a persisted 'nincs mentésre jelölt alkalmazás' run-result is replaced by
  'A kijelölés módosult az utolsó futás óta — a következő távoli mentés már tartalmazza.'
  once ≥1 app is toggled; 0 toggled keeps the v0.123.0 honesty verbatim; every other
  warning (quota, partial) passes through untouched
- replacement renders NEUTRAL (exception-color principle: reassurance, not deviation);
  the untouched original keeps the warn color
- unit + render tests; red-proven (pick removed → 1-enabled case fails at both levels)

controller/internal/web/handlers.go

@@ -653,10 +653,37 @@ func (s *Server) backupsOffboxData(data map[string]interface{}) {
 		}
 	}
 	data["OffboxToggledCount"] = offboxToggled
+	// Part E (v0.126.0): the LastWarning DISPLAY pick — never a state mutation.
+	if offboxTgt != nil {
+		data["OffboxWarningDisplay"] = offboxWarningDisplay(offboxTgt.LastWarning, offboxToggled)
+	} else {
+		data["OffboxWarningDisplay"] = ""
+	}
 	// SLICE 4 soft-quota usage bar (rendered only when a quota is set — shared model).
 	data["OffboxQuotaPct"] = backup.OffboxQuotaPercent(offboxTgt)
 }
 
+// offboxStaleWarningMarker is the substring the zero-toggled offbox run writes into
+// LastWarning (backup/offbox.go); offboxSelectionChangedLine replaces it once the
+// selection has moved on.
+const (
+	offboxStaleWarningMarker   = "nincs mentésre jelölt alkalmazás"
+	offboxSelectionChangedLine = "A kijelölés módosult az utolsó futás óta — a következő távoli mentés már tartalmazza."
+)
+
+// offboxWarningDisplay picks what the Távoli mentés page shows for the persisted
+// Offbox.LastWarning. A zero-toggled run records "Sikeres — nincs mentésre jelölt
+// alkalmazás…"; once the customer HAS toggled apps that line is stale and misleading —
+// replace it with the honest "selection changed, the next run covers it" note.
+// Pure display logic: the persisted LastWarning is never touched, and every other
+// warning (quota, partial failure) passes through verbatim.
+func offboxWarningDisplay(lastWarning string, toggledCount int) string {
+	if toggledCount >= 1 && strings.Contains(lastWarning, offboxStaleWarningMarker) {
+		return offboxSelectionChangedLine
+	}
+	return lastWarning
+}
+
 // backupsHandler renders the Áttekintés page: storage overview, whole-guest Rendszermentés and
 // the status stat cards.
 func (s *Server) backupsHandler(w http.ResponseWriter, r *http.Request) {