Include static files in package build

Add package-data configuration so static files (JavaScript, CSS) are
included when the package is built and deployed. Fixes 404 errors for
datetime-picker.js in production.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pyproject.toml

@@ -38,6 +38,9 @@ animaltrack = "animaltrack.cli:main"
 [tool.setuptools.packages.find]
 where = ["src"]
 
+[tool.setuptools.package-data]
+animaltrack = ["static/**/*"]
+
 [tool.ruff]
 line-length = 100
 target-version = "py311"