feat: added ssl option for database

[scolastico]

Description

This PR adds support for SSL/encrypted database connections. This fixes a bug where the API fails to connect to databases (like DigitalOcean Managed Postgres) that enforce encrypted connections.

Specifically, it:

• Adds DATABASE_SSL and DATABASE_SSL_REJECT_UNAUTHORIZED environment variables to DatabaseConfig.
• Refactors DatabaseService to properly apply SSL settings to the Knex connection object when using pg or mysql modes.
• Ensures only relevant connection properties are passed to Knex for better robustness.

Related Issue

closes not-three/main#28

Checklist

• I have tested my changes locally (via build and linting)
• I have updated the documentation if needed (configuration model updated)
• This PR follows the project's coding style

Additional Notes

Users can now enable SSL by setting DATABASE_SSL=true. If using self-signed certificates or certain managed providers, DATABASE_SSL_REJECT_UNAUTHORIZED=false may also be required.