feat: add support for additional DNS names in SAN

Changes:
- generate-csr.sh: New 9th parameter for comma-separated additional DNS names
- cert-manager.py: Interactive prompt for additional DNS names
- Automatically appends extra names to SAN list

Example usage:
- Interactive: Enter 'firewall.domain.com,vpn.domain.com' at prompt
- Manual: ./generate-csr.sh host fqdn DE berlin berlin org it 4096 'extra1.com,extra2.com'

Benefits:
✅ Single certificate for multiple DNS names
✅ Support for aliases and CNAMEs
✅ Flexible certificate deployment

cert-manager.py

@@ -173,6 +173,11 @@ def main():
     print(f"✓ Detected: {system_info['name']}")
     
     common_name = prompt_with_default("Common Name (FQDN)", config['last_common_name'])
+
+    # Ask for additional DNS names
+    print("\nAdditional DNS names (optional, comma-separated):")
+    print("  Example: firewall.domain.com,vpn.domain.com")
+    additional_dns = input("Additional DNS names [none]: ").strip()
     
     if not common_name:
         print("Error: Common name is required!")
@@ -197,6 +202,8 @@ def main():
     print(f"System Type:     {system_info['name']}")
     print(f"Target Host:     {target_host}")
     print(f"Common Name:     {common_name}")
+    if additional_dns:
+        print(f"Additional DNS:  {additional_dns}")
     print(f"Country:         {country}")
     print(f"State:           {state}")
     print(f"Locality:        {locality}")
@@ -232,7 +239,8 @@ def main():
         locality,
         organization,
         org_unit,
-        key_bits
+        key_bits,
+        additional_dns
     ]
     
     try: