Enable new types of absence in absence planner

[kusalananda]

Please describe the feature

As a user, I want to be able to pick any of the current types of absences in the absence planner.

Detailed description

In its current incarnation, the absence planner allows one to add one's absence with one of the following types:

• Parental leave
• Sick leave
• VAB
• Vacation
• Other

During 2024, several other absence types were added, e.g. "Red days" (issue number 7450; but there are others). The available absence types should be mirrored in the drop-down list in the absence planner.