Add comprehensive test suite for improved code reliability

[HarshavardhanVemali]

Problem

The Hiring Agent project currently lacks test coverage, which poses risks for:

• Code reliability and regression prevention
• Confident refactoring and feature development
• Code quality assurance
• Future contributor onboarding

Proposed Solution

Implement a comprehensive test suite including:

• Unit tests for all Pydantic models and core utilities
• Integration tests for the complete pipeline workflow
• Performance tests for optimization opportunities
• CI/CD pipeline with automated testing
• Test fixtures and utilities for maintainable tests

Benefits

• Ensures code reliability and prevents regressions
• Enables confident future development
• Provides immediate feedback through CI/CD
• Sets standard for future contributions
• Improves overall code quality

Implementation Plan

1. Unit tests for models.py and llm_utils.py
2. Integration tests for end-to-end workflow
3. Performance tests for optimization
4. CI/CD pipeline configuration
5. Test documentation and utilities

This addresses a critical gap in the project's infrastructure and follows software engineering best practices.

[HarshavardhanVemali]

I'm working on this