ADR on contract-first approach

[katariniss]

During joint reviews, we decided to implement a new design approach.
Flow:

1. design and agree on a contract ->
2. deploy the contract to the back-end to unlock the front-end ->
3. discuss and agree on how we want to test the new functionality ->
4. write happy path E2E tests ->
5. and only then begin implementation

This way, we will develop design skills, which are becoming increasingly valuable in the era of rapid AI development.