v0.14.1: Auto Tier 2 for small apps + infra config in cross-drive backup

- Auto-enable daily rsync Tier 2 for apps without HDD mounts when ≥2
  storage paths exist (AutoEnableSmallApps)
- Sync infrastructure config (stacks dir + controller.yaml) to all
  secondary destinations via _infra/ directory (syncInfraConfig)
- Include infra paths in cross-drive restic snapshots
- Add SecondaryInfraPath() helper to paths.go

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/cmd/controller/main.go

@@ -132,7 +132,7 @@ func main() {
 	}
 
 	// --- Initialize cross-drive backup runner ---
-	crossDriveRunner := backup.NewCrossDriveRunner(sett, stackProv, cfg.Paths.SystemDataPath, logger)
+	crossDriveRunner := backup.NewCrossDriveRunner(sett, stackProv, cfg.Paths.SystemDataPath, cfg.Paths.StacksDir, logger)
 
 	// Wire cross-drive → backup manager for pre-backup DB dumps
 	if backupMgr != nil {