Add comprehensive RSS scraper implementation with security and testing

- Modular architecture with separate modules for scraping, parsing, security, validation, and caching
- Comprehensive security measures including HTML sanitization, rate limiting, and input validation
- Robust error handling with custom exceptions and retry logic
- HTTP caching with ETags and Last-Modified headers for efficiency
- Pre-compiled regex patterns for improved performance
- Comprehensive test suite with 66 tests covering all major functionality
- Docker support for containerized deployment
- Configuration management with environment variable support
- Working parser that successfully extracts 32 articles from Warhammer Community

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -1,4 +1,15 @@
 *.xml
 .python-version
 output/
-output/*
+output/*
+cache/
+*.log
+__pycache__/
+*.pyc
+*.pyo
+.pytest_cache/
+.coverage
+htmlcov/
+.env
+.venv/
+venv/