Updates copyright to 2026

Fixes CPU check failing on certain machines with error "Divided by 0"

Updates changelog release date

Adds migration tasks for v1.13.5

Adds migration tasks to v1.12.5

Fixes security issue by restricting access to core folders of Icinga …

…for Windows for generic users

Fixes security issue by restricting access to core folders of Icinga …

…for Windows for generic users

Fixes security issue by restricting access to core folders of Icinga …

…for Windows for generic users

Fixes changelog

Fixes IfW service installation on certain Windows environment