chore: add comprehensive pytest configuration and test infrastructure

[1234-ad]

Summary

Adds comprehensive pytest configuration and testing infrastructure with GitHub Actions integration.

Changes

pytest.ini

• Test discovery patterns for consistent test detection
• Multiple coverage report formats (terminal, HTML, XML)
• Coverage threshold set to 60% with fail-under enforcement
• Custom test markers for categorization:
  • unit: Unit tests
  • integration: Integration tests
  • slow: Slow running tests
  • discord: Discord bot tests
  • github: GitHub integration tests
  • ai: AI/ML tests
  • requires_api: Tests requiring external APIs
• Coverage exclusions for config, deployment, and test files
• Detailed output with durations and short tracebacks

.github/workflows/test-suite.yml

• Matrix testing across Python 3.11, 3.12, and 3.13
• Separate unit and integration test runs
• Code coverage tracking with Codecov integration
• Linting and formatting checks (black, flake8, isort)
• Security scanning with bandit
• Coverage reports and artifacts upload

Benefits

• ✅ Standardized testing across the project
• ✅ Clear test categorization with markers
• ✅ Coverage tracking and reporting
• ✅ CI/CD ready configuration
• ✅ Multi-version Python compatibility verification
• ✅ Automated code quality enforcement
• ✅ Security vulnerability detection

Usage

# Run all tests
pytest

# Run only unit tests
pytest -m unit

# Run with coverage
pytest --cov

# Run specific test categories
pytest -m "github and not slow"

Testing

• Configuration validated with pytest 8.x
• Compatible with existing test structure
• Tested with Python 3.11, 3.12, and 3.13

Impact

• Enables systematic testing approach
• Improves code reliability
• Catches regressions early
• Provides clear test organization