Fix CSS326 support

[vvbelousov]

Fix CSS326 support: correct SwOS detection + clean VLAN export

• fix platform detection (CSS326 runs SwOS, not SwOS Lite)
• stop treating all CSS models as SwOS Lite
• fix export logic: vlan_mode=Optional is baseline, not a change

Result: correct detection and no noisy port_vlans in export.
Tested on:

• CSS326-24G-2S+ (SwOS 2.18)
• CRS310-8G+2S+ (SwOS 2.18)

[Dennis-Q]

This is great work, I tested it on my CSS318 which also runs SWoS not Lite, and seems to work perfectly:

Connecting to switch at http://XXX.XXX.XXX.XXX...
Username: admin

Retrieving system information...

================================================================================
  SYSTEM INFORMATION
================================================================================

  Device Model:  CSS318-16G-2S+
  Device Name:   N/A
  Version:       2.18
  Serial Number: XXXXXXXXXX
  MAC Address:   xx:xx:xx:xx:xx:xx
  Uptime:        129532556 seconds

For others that don't like to wait for the request to be merged:

1. Put this line into your requirements.txt
   git+https://github.com/lanrat/python-mikrotik-swos.git@refs/pull/4/head
2. Then run this command:
   pip install --upgrade --force-reinstall -r requirements.txt

Ignore any Did not find branch or tag 'refs/pull/4/head', assuming revision or ref. errors, they are expected. Then you can try something like: swos-config 192.168.88.1 admin "". In my case, it gave me back switch info, but also port and VLAN information.

Thank you @vvbelousov !