FEATURE: Remove compiled assets from Repository

[jrenggli]

Currently there are compiled assets in Resources/Public/Assets folder, e.g.

main.bundle.css (58K)
main.bundle.css.map (80K)
main.bundle.js (1.2M)
main.bundle.js.map (7.1M)

This leads to the following issues:

• Unclear contribution workflow: developers don't know whether the compiled assets should be included in commits / merge requests or not. (They shouldn't. 😉)
• Every change adds ~9 MB of binary churn to the repository, causing the repo size to grow indefinitely.
• Diffs on bundle files are noisy and add no review value.

Goal is to remove compiled assets and add a way to generate these only on tag creation via GitHub Action.

[jrenggli]

While working on this issue I discovered outdated dependencies and refused to use these for the new workflow.
The keep consistency I created another PR to update these for tests.yaml. See #290

Also yarn installs should IMHO be immutable. See PR #291