Add support to Debian 13 Trixie as NS8 base OS

[mrmarkuz (Markus Neuberger)]

Check out the Debian Upgrade Howto:

Upgrade Debian 12 to 13

Hi Debian admins, Debian 13 Trixie is out since 2025-08-09 and NS8 migration from Debian 12 to 13 should be possible now. Please test the upgrade procedure on your Debian systems. Core 3.17 is required. We would like to introduce a testing period until June for this upgrade procedure. In this period both, Debian 12 and 13 will be supported. After the Testing phase, only Debian 13 will be supported. Support for 12 will be removed from the installer. Migration steps from Debian 12 to 13 Don’t…