Allow hostname to be FQDN

[HeMan]

✍️ Description

🔗 Related Issue

Fixes #

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

---

🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.

[MickLesk]

It incorrectly allows:

• test..example (double dots)
• test.-example (dot + hyphen)
• test. (trailing dot)

Only 1 label, max 63 characters total (not RFC-compliant)

Hostname: max. 63 characters, no dots
FQDN: Multiple labels with dots, each label max. 63 characters, total max. 253 characters

[HeMan]

Should the check be fully FQDN compliant and allow capital letters as well?

[MickLesk]

should be like this:

# ...existing code...
    if result=$(whiptail --backtitle "Proxmox VE Helper Scripts [Step $STEP/$MAX_STEP]" \
      --title "HOSTNAME" \
      --ok-button "Next" --cancel-button "Back" \
      --inputbox "\nSet Hostname (or FQDN, e.g. host.example.com)" 10 58 "$_hostname" \
      3>&1 1>&2 2>&3); then
      local hn_test="${result:-$NSAPP}"
      hn_test=$(echo "${hn_test,,}" | tr -d ' ')
      
      # Validate hostname/FQDN according to RFC 1123/952
      local valid=true
      
      # Check total length (max 253 for FQDN)
      if [[ ${#hn_test} -gt 253 ]]; then
        valid=false
      fi
      
      # Split by dots and validate each label
      if $valid; then
        IFS='.' read -ra labels <<< "$hn_test"
        for label in "${labels[@]}"; do
          # Each label: 1-63 chars, alphanumeric, hyphens allowed (not at start/end)
          if [[ -z "$label" ]] || [[ ${#label} -gt 63 ]]; then
            valid=false
            break
          fi
          if [[ ! "$label" =~ ^[a-z0-9]([a-z0-9-]*[a-z0-9])?$ ]] && [[ ! "$label" =~ ^[a-z0-9]$ ]]; then
            valid=false
            break
          fi
        done
      fi
      
      if $valid; then
        _hostname="$hn_test"
        ((STEP++))
      else
        whiptail --msgbox "Invalid hostname: '$hn_test'\n\nRules:\n- Only lowercase letters, digits, dots and hyphens\n- Labels separated by dots (max 63 chars each)\n- No leading/trailing hyphens or dots\n- No consecutive dots\n- Total max 253 characters" 14 60
      fi
# ...existing code...

its a little bit more then 2-4 changed lines