CHORE: Make Readme more concise and reference docs

[mberz]

This pull request significantly refactors and updates the README.md to provide a clearer, more concise overview of the CHORAS backend. The new README improves project documentation, highlights CI/CD and documentation status, and streamlines setup and contribution guidelines.

Documentation and Project Overview:

• Added CI/CD and documentation status badges at the top for better project visibility.
• Simplified and clarified the project description, focusing on core responsibilities and integration requirements.

Technology Stack and Features:

• Updated and reorganized the technology stack section for clarity, combining related items and correcting naming conventions (e.g., Flask-SQLAlchemy, Flask-Migrate).
• Explicitly listed Celery as the job queue system.

Setup and Contribution:

• Removed outdated environment setup, deployment, and command instructions, instead directing users to the documentation pages for setup and to the contributing guide for community involvement.