- add pyproject.toml
- declare runtime dependencies
- add pytest, ruff, mypy and pylint
- configure src layout
- keep existing removeads.py behavior unchanged
refactor: extract H.264 bitstream primitives
refactor: extract SPS/PPS structures
refactor: extract AVC decoder configuration
refactor: extract Matroska/EBML helpers
refactor: isolate external tool execution
refactor: separate CLI from processing pipeline