feat: set_hostname — update /etc/hostname, /etc/hosts, cert, Postfix

Implements set_hostname on ProxmoxSystemMixin:
1. Writes /etc/hostname (short name, base64-safe transfer)
2. Replaces old hostname in /etc/hosts via Python regex + base64
3. Updates /etc/mailname if present
4. Updates Postfix myhostname via postconf -e if installed
5. Applies hostname immediately at runtime via hostname(1)
6. Regenerates Proxmox node TLS certificate via pvecm updatecerts -f
   (falls back to pvenode cert create → pveproxy restart)

Accepts bare hostname or FQDN. A reboot is required for the Proxmox
node name to update in the web UI / cluster — the driver logs this.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

napalm_proxmox/utils.py

@@ -26,28 +26,6 @@ _MAC_RE = re.compile(
 
 
 def normalize_mac(mac: str) -> str:
-    """Return a colon-separated, lower-case MAC address, or '' on failure."""
-    if not mac:
-        return ""
-    try:
-        return str(EUI(mac, dialect=_ColonDialect()))
-    except (AddrFormatError, ValueError):
-        return mac.lower()
-
-
-class _ColonDialect(EUI):
-    """EUI dialect that formats as aa:bb:cc:dd:ee:ff."""
-
-    word_sep = ":"
-    word_fmt = "%.2x"
-
-    def __new__(cls):  # type: ignore[override]
-        from netaddr import mac_unix_expanded
-
-        return mac_unix_expanded
-
-
-def normalize_mac(mac: str) -> str:  # noqa: F811
     """Return lower-case colon-separated MAC or empty string."""
     if not mac:
         return ""