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/interactive.go

@@ -37,16 +37,16 @@ func interactiveEdit(hosts []Host, name string, cfg netConfig) ([]Host, error) {
 	var cur Host
 	if idx >= 0 {
 		cur = hosts[idx]
-		fmt.Printf("Bearbeite bestehenden Host %q (Enter = Wert behalten)\n", name)
+		fmt.Printf("Editing existing host %q (press enter to keep a value)\n", name)
 	} else {
 		cur = Host{Name: name}
-		fmt.Printf("Neuer Host %q (Enter bei MAC/Comment = leer lassen)\n", name)
+		fmt.Printf("New host %q (press enter to leave MAC/comment empty)\n", name)
 	}
 
 	for {
-		ip := prompt("IP-Adresse", cur.IP)
+		ip := prompt("IP address", cur.IP)
 		if err := validateIP(ip, cfg.lanCIDR, cfg.poolStart, cfg.poolEnd); err != nil {
-			fmt.Fprintln(os.Stderr, "Fehler:", err)
+			fmt.Fprintln(os.Stderr, "error:", err)
 			continue
 		}
 		cur.IP = ip
@@ -54,26 +54,26 @@ func interactiveEdit(hosts []Host, name string, cfg netConfig) ([]Host, error) {
 	}
 
 	for {
-		mac := prompt("MAC-Adresse (optional, '-' zum Löschen)", macOrDash(cur.MAC))
+		mac := prompt("MAC address (optional, '-' to clear)", macOrDash(cur.MAC))
 		if mac == "-" {
 			mac = ""
 		}
 		norm, err := normalizeMAC(mac)
 		if err != nil {
-			fmt.Fprintln(os.Stderr, "Fehler:", err)
+			fmt.Fprintln(os.Stderr, "error:", err)
 			continue
 		}
 		cur.MAC = norm
 		break
 	}
 
-	cur.Comment = prompt("Kommentar", cur.Comment)
+	cur.Comment = prompt("Comment", cur.Comment)
 
 	if other := findByIP(hosts, cur.IP, idx); other >= 0 {
-		return nil, fmt.Errorf("IP %s ist bereits Host %q zugewiesen", cur.IP, hosts[other].Name)
+		return nil, fmt.Errorf("IP %s is already assigned to host %q", cur.IP, hosts[other].Name)
 	}
 	if other := findByMAC(hosts, cur.MAC, idx); other >= 0 {
-		return nil, fmt.Errorf("MAC %s ist bereits Host %q zugewiesen", cur.MAC, hosts[other].Name)
+		return nil, fmt.Errorf("MAC %s is already assigned to host %q", cur.MAC, hosts[other].Name)
 	}
 
 	if idx >= 0 {