Add a simple helm chart

The purpose of this MR is to propose basic helm chart. Ultimately the helm chart is responsibility of the subsystem, since it's design implies familiarity with the app design, structure, and whatever plans for the future are in place.

The MR does not add much beyond what is already in the repository except for the chart. It does add integration test from readme in the helm test. If further changes are needed for verification we must discuss, probably best in separate issue/MR.

While making this basic chart I am trying to avoid any changes to the code, but there are some questions that come up while making this chart, specifically relevant for deployment.

The points below should probably be addressed either here or in follow-up issues.

• frontend app deployment is very similar to backend, if they will remain like that, they might be templated to avoid duplication. Just for my information, since they are both FastAPI, why are they split? I am use to see backend in FastAPI and frontend in some JS frontend framework - then split is natural.
• nginx pod is not needed if it remains limited to redirecting two paths: this can be done by the ingress controller
• containers seem to have dev requirements, always copied, I suppose this should be optional, even if it's just a file
• if you want to keep compose setup in parallel to the one of helm, you'll need to constantly keep them in sync. In all other cases we dropped compose setup entirely
• try to add annotation with xray interface

Notes for verification later:

• normally we deduplicate tests, but e2s playwrite e2e tests are duplicate in the sense used there. For now I restrict to one browser, but we need to see how we show different tests which are identical in "normal" sense.
• junit from playwrite does not have properties linking UCs/Req which we use for verification (like here). If these tests are to be linked to UCs, we need to find a way to put these properties.

Closes #8 (closed)