Add mypy

[hugovk]

Still some things to fix, so not in CI yet.

❯ tox -e mypy
.pkg: _optional_hooks> python /Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/site-packages/pyproject_api/_backend.py True hatchling.build
.pkg: get_requires_for_build_sdist> python /Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/site-packages/pyproject_api/_backend.py True hatchling.build
.pkg: build_sdist> python /Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/site-packages/pyproject_api/_backend.py True hatchling.build
mypy: install_package> python -I -m pip install --force-reinstall --no-deps /Users/hugo/github/osmviz/.tox/.tmp/package/11/osmviz-4.4.1.dev23.tar.gz
mypy: commands[0]> mypy .
src/osmviz/animation.py:367: error: Incompatible types in assignment (expression has type "float", variable has type "int")  [assignment]
src/osmviz/animation.py:369: error: Incompatible types in assignment (expression has type "float", variable has type "int")  [assignment]
examples/pil_example.py:16: error: Module has no attribute "ANTIALIAS"  [attr-defined]
examples/custom_animations.py:50: error: Argument 3 to "line" has incompatible type "None"; expected "tuple[float, float] | Sequence[float] | Vector2"  [arg-type]
examples/custom_animations.py:50: error: Argument 4 to "line" has incompatible type "None"; expected "tuple[float, float] | Sequence[float] | Vector2"  [arg-type]
Found 5 errors in 3 files (checked 11 source files)
mypy: exit 1 (0.82 seconds) /Users/hugo/github/osmviz> mypy . pid=41690
.pkg: _exit> python /Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/site-packages/pyproject_api/_backend.py True hatchling.build
  mypy: FAIL code 1 (2.78=setup[1.96]+cmd[0.82] seconds)
  evaluation failed :( (2.89 seconds)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.18%. Comparing base (264e5c9) to head (22f54c0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #95   +/-   ##
=======================================
  Coverage   55.18%   55.18%           
=======================================
  Files           6        6           
  Lines         453      453           
=======================================
  Hits          250      250           
  Misses        203      203           

Flag	Coverage Δ
macos-latest	55.18% <100.00%> (ø)
ubuntu-latest	55.18% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.