ipadm: translate to English, fix help alignment

- All ipadm-internal messages (usage, prompts, errors) are now English
- Usage text is built programmatically from a (left, desc) row list with
  computed column width instead of hand-aligned spaces, so it can't drift
  out of alignment again when rows are added/changed
- README's literal usage block updated to match; rest of the repo docs
  stay German

tools/ipadm/nftpf.go

@@ -25,7 +25,7 @@ func renderPortForwards(hosts []Host, fwds []PortForward, wanIface string) (cont
 	for _, f := range sorted {
 		ip, ok := ipByHost[strings.ToLower(f.Host)]
 		if !ok {
-			warnings = append(warnings, fmt.Sprintf("Port-Forward %d/%s -> %q übersprungen: Host nicht (mehr) in der ipadm-Datenbank", f.WanPort, f.Proto, f.Host))
+			warnings = append(warnings, fmt.Sprintf("port-forward %d/%s -> %q skipped: host no longer in the ipadm database", f.WanPort, f.Proto, f.Host))
 			continue
 		}
 		switch f.Proto {
@@ -58,14 +58,14 @@ func applyPortForwards(path string, content string) error {
 		backup = b
 		hadFile = true
 	} else if !os.IsNotExist(err) {
-		return fmt.Errorf("kann bestehende %s nicht lesen: %w", path, err)
+		return fmt.Errorf("cannot read existing %s: %w", path, err)
 	}
 
 	if err := os.MkdirAll(dirOf(path), 0755); err != nil {
-		return fmt.Errorf("kann Verzeichnis für %s nicht anlegen: %w", path, err)
+		return fmt.Errorf("cannot create directory for %s: %w", path, err)
 	}
 	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
-		return fmt.Errorf("kann %s nicht schreiben: %w", path, err)
+		return fmt.Errorf("cannot write %s: %w", path, err)
 	}
 
 	if err := runNftTest(); err != nil {
@@ -74,11 +74,11 @@ func applyPortForwards(path string, content string) error {
 		} else {
 			os.Remove(path)
 		}
-		return fmt.Errorf("nftables-Konfiguration ungültig, Änderung zurückgerollt: %w", err)
+		return fmt.Errorf("nftables config invalid, change rolled back: %w", err)
 	}
 
 	if err := reloadNftables(); err != nil {
-		return fmt.Errorf("%s geschrieben, aber Reload fehlgeschlagen: %w", path, err)
+		return fmt.Errorf("%s written, but reload failed: %w", path, err)
 	}
 	return nil
 }