[FEATURE REQUEST] (Update only when admin password is set)

### Please confirm these before moving forward.

- [x] I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue.
- [x] This proposal is a completely new feature. If you want to suggest an improvement or an enhancement, please use [this template](https://github.com/Devolutions/UniGetUI/issues/new?labels=enhancement&projects=&template=enhancement-improvement.yml&title=%5BENHANCEMENT%5D+%28Enter+your+description+here%29).

### Describe the new feature

If admin password is set on install then the program will run as update existing programs only, hiding all other options.

### Describe how this new feature could help users

Useful in a company, where sysadmin wants to allow a user to update existing programs but not install new ones,