Implement asynchronous database initialization: add init_db function to create collections and indexes in MongoDB, update get_db to support async, and modify main.py to await database initialization during startup.

Update requirements and enhance MongoDB connection: add certifi dependency for SSL configuration and modify connection settings for improved security and reliability.

Refactor database management to use MongoDB with async support; update audiobook routes for MongoDB integration and improve error handling.

Refactor application structure: rename 'models' directory to 'db_models', update import paths across multiple files, and enhance Dockerfile to create and populate the new directory, improving organization and clarity in the codebase.

Refactor model structure: update import paths from 'app.modelz' to 'app.models' across multiple files for consistency, remove obsolete 'modelz' directory, and adjust Dockerfile and migration script to reflect these changes, enhancing clarity and organization in the codebase.

Refactor application structure: update model import paths from 'app.model' to 'app.modelz' across multiple files for consistency, and introduce new database models in 'app.modelz.database' to enhance organization and clarity in the codebase.

Refactor imports across application files: update model import paths from 'app.models' to 'app.model' for consistency and clarity, ensuring correct module references throughout the codebase.

Update Alembic configuration and migration scripts: change script location and version path in alembic.ini, add env.py for migration management, create initial migration script for audiobooks table, and implement migration execution in a new migrate.py script.

Initialize database and add storage directories; include audiobook routes