Release 4.13.0

• Improved task handling in the Today view, including real-time updates and midnight refresh fixes - thanks to @igor-semenov.
• Nextcloud login flow redesigned for better UX and stability - thanks to @byquanton.
• Fixed crashes caused by UTF-8 character handling - thanks to @byquanton.
• Russian translation added — thanks to @Heinrich-XIAO.
• Refactored utility methods and internal cleanup.