R-488: backup tests read ONE health-wait clock; package 444 s -> ~2 s

waitForHealthy's 3 s settle / 5 s poll / 90 s timeout become package vars (production values
unchanged, pinned by TestR488_HealthWaitDefaultsAreProduction); TestMain shortens them once.
Measured before: 51 of 599 tests held 442 of 444 s, two not-running fixtures 279 s alone.
newOffboxManager now installs a failing SSH fake: TestOffbox_ConfirmedReset was spawning a
real 'ssh felhom@nas.local' and waiting out its 10 s ConnectTimeout.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/backup/tier2_restore.go

@@ -440,7 +440,7 @@ func (m *Manager) RestoreTier2Files(stackName string) (filesRestored int, err er
 	if startErr != nil {
 		m.logger.Printf("[ERROR] [backup] failed to restart %s after Tier-2 file restore: %v", stackName, startErr)
 	}
-	if healthErr := m.waitForHealthy(stackName, 90*time.Second); healthErr != nil {
+	if healthErr := m.waitForHealthy(stackName, healthTimeout); healthErr != nil {
 		m.logger.Printf("[WARN] [backup] %s Tier-2 file restore done but health check failed: %v", stackName, healthErr)
 	}