Add Seeder and Migration Support with Multi-Database Compatibility

Currently, Servitect focuses on generating a backend server with MongoDB as the default database. To make the tool more flexible and robust, the following enhancements are proposed:

Seeder and Migration Support:

1. _Add functionality to generate seed files for populating databases with dummy data._
Include a migration system to handle database schema updates easily.
Multi-Database Compatibility:

2. _Provide support for multiple databases, including **PostgreSQL**, **MySQL**, and **SQLite**, in addition to MongoDB._

3. Allow developers to _choose the database during initialization via the CLI._

4. _Seamless Integration:_
Ensure seed and migration scripts are compatible with all supported databases.
Provide clear documentation and examples for using these features.
This enhancement will enable Servitect to cater to a broader range of projects and developers by supporting diverse database ecosystems and simplifying database management.

Start by reading Servitect's CLI initialization flow and the generated backend structure. Map how MongoDB is currently configured, then define the scope for database selection, seed files, migrations, and documentation across MongoDB, PostgreSQL, MySQL, and SQLite. Done means the requested databases can be selected during initialization and the generated seed and migration features are documented with examples.

Written by the indexing model from the issue text.