chore: openspec setup

[jesmrec]

Related Issues

App:

• Add changelog files for the fixed issues in folder changelog/unreleased. More info here
• Add feature to Release Notes in ReleaseNotesViewModel.kt creating a new ReleaseNote() with String resources (if required)

---

QA

[jesmrec]

Things to add/check:

• context: review, content should be similar to the AGENTS.md

• rules: how the artifacts should be generated. The key issue is tasks where all implementation rules should be set.

• operations: basic review