How to maintain `FEATURES.md`:

* **If absent**, create with:

  * TOC
  * For each feature:

    * Creation date
    * Description
    * Dependencies
    * Files (with brief roles)

* **If present**, update by adding, modifying, or removing features accordingly.

* **Questions this document must be able to answer**:

  1. What are the core features delivered by this project?
  2. When was each feature introduced?
  3. What user needs or use cases does each feature address?
  4. What files implement or support each feature?
  5. What dependencies are required for each feature to work?
  6. Are features toggled via environment variables or config?
  7. Which features are user-facing vs backend-only?
  8. What is the data flow for each feature?
  9. Are there any permissions or roles tied to features?
  10. Is the feature always active or conditional?
  11. Is the feature part of an MVP or roadmap item?
  12. How do features relate to external services?
  13. Are any features deprecated or under rework?
  14. How are edge cases handled per feature?
  15. What tests validate each feature?
  16. Are there known limitations per feature?
  17. Which features are reusable or shared across contexts?
  18. Does this feature require localization or regional logic?
  19. Are any features monetized or gated?
  20. What business logic does each feature encapsulate?