Feat/employer candidate shortlisting stage5

[igbonekwu-joy]

Description

This PR adds the employer candidate shortlist MVP in the employer module. Authenticated employers can save Job Ready talent for later review, list saved candidates, and remove them. The work follows the shortlist RFC and the employer module layout: controller, service, repository, and talent lookup. This is strictly for my stage 5 BE task.

Related Issue (Link to Github issue)

N/A

Motivation and Context

How Has This Been Tested?

Automated tests
There are no unit or e2e tests that call the shortlist endpoints or assert shortlist behavior.

pnpm test:e2e still runs three suites:

test/app.e2e-spec.ts — health and probe only
test/auth.e2e-spec.ts — auth flows only
test/onboarding.e2e-spec.ts — talent and employer onboarding only

Screenshots (if appropriate - Postman, etc): N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• [✓ ] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [✓ ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [✓ ] I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• [✓ ] All new and existing tests passed.