chore: migrate to Python 3.13 + hatchling + uv, modernize toolchain

[chenailin11]

Build system:

• Replace setup.py/pbr/tox with hatchling + uv (pyproject.toml)
• Add uv.lock for reproducible installs
• Version single-sourced from yabgp/init.version
• Add PEP 735 dependency-groups: test, dev, docs

CI & Docker:

• GitHub Actions: switch to uv sync + uv run pytest/ruff/pyright
• Add windows-latest to CI matrix (ubuntu/macos/windows)
• Dockerfile: migrate from pip to uv sync --locked --no-dev
• Add .dockerignore to exclude .venv/.git/.claude/tools/doc from image

Lint & type check:

• Replace flake8 with ruff (E/W/F/I/UP, line-length=120, py313)
• Add pyright (typeCheckingMode=off, reportDeprecated=error)
• Fix 300+ lint issues across src and tests (auto-fix + manual)

Bug fixes:

• Use integer division // instead of / in community/largecommunity parse to avoid intermediate float values (len(value)//2, len(value)//4)

Cleanup:

• Remove setup.py, setup.cfg, tox.ini, .coveragerc, .testr.conf
• Remove requirements.txt, test-requirements.txt (superseded by uv.lock)
• Remove redhat/, run_test.py, tools/rabbit_mongo.sh, yabgp/hooks.py
• Migrate .coveragerc into pyproject.toml [tool.coverage.run]

Docs:

• Update README/HACKING.rst to uv-based workflow
• Update doc/source/install.rst and feature/extension/tutorial pages
• Bump docs deps: sphinx>=8, sphinx-rtd-theme>=3 via dependency-group

Verified: 284 unit tests pass; BGP-LS RIB output identical between py3.6 and py3.13 against live router (node/link/prefix/srv6_sid).