Create mock tests that don't require API credentials

[devondragon]

Current tests require actual API credentials. This issue proposes adding mock-based tests.

Proposed Changes

• Implement mock responses for OpenAI API
• Create test fixtures for common test scenarios
• Add tests that run without requiring API credentials
• Ensure CI pipeline can run tests without credentials

Benefits

• Makes it easier to contribute to the project
• Enables CI testing without exposing credentials
• Provides faster test execution