Add signed release builds for CI

[Luc1412]

The CI could be drastically improved by by building signed, upload ready artifacts. (IPA, Appbundle) These artificats also could be automatically released for internal test group. We got various things to keep in mind:

• Should normal builds on commit/pr be signed release builds or do we keep them as debug builds?
• We probably want to trigger uploads only when creating a release
• We need to manage the build number. Possible incrementing it automatically