fix: Preparing hotfix release 1.5.6 fixing three issues

[buhtz]

Fix or workaround this three issues:

• Always use 0 as window ID value when inhibiting suspend via D-Bus power manager (Remove window-id use (was: I updated EndeavourOS on Sunday. After the update, attempting restore in BiT fails - the window closes). #2084, fix-UInt32-overflow in common/tools.py #2268, Manually removing a snapshot in the GUI does not work (xwindowid problem) #2192)
• Crash in "Manage profiles" dialog when using "qt6ct" (Crashes ("TypeError: standardPixmap(...") when running with qt6ct and Breeze theme #2128)
• Open online changelog if local CHANGES file is missing (Clicking Help + Changelog crashes (Debian 13, BIT 1.5.5) #2266)

The purpose release 1.5.6 with minimum changes possible compared to 1.5.5 to make it into current Debian stable.

Close #2258