Release v0.1.2: Dual-Engine SVG Rendering Architecture

Added:
- Integrated `resvg-py` as primary production SVG renderer (required)
- Pure-Python engine as fallback for edge cases
- Engine parameter (auto/resvg/python) in convert() and CLI
- Comprehensive test suites for format conversions and real logos
- HTML report generation for visual validation
- CHANGELOG.md and PUBLISHING.md documentation

Changed:
- `resvg-py` is now a core dependency (installed automatically)
- SVG rendering defaults to resvg with automatic fallback to Python
- Removed debug print statements for cleaner production output

Technical:
- Added svg/engines/ architecture with base classes
- 100% success on real-world logo tests
- 82.4% success on comprehensive format tests
