Add Support for CS Master

[lucakbb]

To make it possible for CS Master students to plan their studies in the app, the following features are required:

• Ask during onboarding whether you are a Bachelor's or Master's student. Additionally, let them choose major and minor
• Be able to switch between Master and Bachelor in the settings. You should also be able to change the major and minor here
• Create correct categories
• Adjust credit calculation and graduation requirements
• Scrape courses from VVZ. For core courses and electives, add the corresponding major and minor as a tag.
• Update the core data model to indicate whether it is a Bachelor's or Master's course. You should be able to switch between them without having to delete all the data.
• Add a new filter for courses to filter for major and minor when adding or searching for them. By default, this filter should align with the preferences set during Onboarding or in the Settings.