fix: dynamic timeouts for large archives + use WorkDir for disk checks

- CheckDiskSpace now uses GetEffectiveWorkDir() instead of BackupDir
- Dynamic timeout calculation based on file size:
  - diagnoseClusterArchive: 5 + (GB/3) min, max 60 min
  - verifyWithPgRestore: 5 + (GB/5) min, max 30 min
  - DiagnoseClusterDumps: 10 + (GB/3) min, max 120 min
  - TUI safety checks: 10 + (GB/5) min, max 120 min
- Timeout vs corruption differentiation (no false CORRUPTED on timeout)
- Streaming tar listing to avoid OOM on large archives

For 119GB archives: ~45 min timeout instead of 5 min false-positive

internal/restore/safety.go

@@ -229,8 +229,14 @@ func containsSQLKeywords(content string) bool {
 }
 
 // CheckDiskSpace verifies sufficient disk space for restore
+// Uses the effective work directory (WorkDir if set, otherwise BackupDir) since
+// that's where extraction actually happens for large databases
 func (s *Safety) CheckDiskSpace(archivePath string, multiplier float64) error {
-	return s.CheckDiskSpaceAt(archivePath, s.cfg.BackupDir, multiplier)
+	checkDir := s.cfg.GetEffectiveWorkDir()
+	if checkDir == "" {
+		checkDir = s.cfg.BackupDir
+	}
+	return s.CheckDiskSpaceAt(archivePath, checkDir, multiplier)
 }
 
 // CheckDiskSpaceAt verifies sufficient disk space at a specific directory