feat(estimation-service): implement Clean Architecture with Redis and SQLite repositories

[Rustixir]

feat(estimation-service): implement Clean Architecture with Redis and SQLite repositories

Document Location: ./docs/README.md

PR Description:

• Describe the key changes in your PR:
  - This PR adds the following features:
  * Redis-based repository with ZAdd for user segments.
  * SQLite-based repository using Ent ORM.
  * Accept-Language middleware to detect user-preferred language.
  * Cleanup worker for removing expired users (Redis and SQLite).
  * Unit tests for repository logic and integration tests for API endpoints.
  * Error handler with localization support.

All changes follow clean architecture and SOLID principles, ensuring testability and flexibility.