add the existing email routes and handler to the API

[williamchiii]

Description

This wires the existing email API endpoints located in apps/api/internal/domains/email/http.go (lines 14 - 58) into the main API router locaed in apps/api/internal/api/api.go.

The email handlerrs and routes were already implemented, but were not registered in the main API router.

Type of Change

• Bug fix (non-breaking change)

Checklist

• My code follows the project's style guidelines
• I have commented on complex parts of the code (the change was not complex)
• I have updated documentation if necessary
• I have updated or added tests to cover my changes
• I have updated the OpenAPI YAML or other API schema files if applicable

Additional Notes

Previously, the existing email handlers and routes were not reachable in the main api router, and as a result, they did not appear in the OpenAPI docs. This PR adds the existing email handlers into the main api router.

This change allows these endpoints to be reached: