Update CI/CD workflows to use `uv`

• also, remove MANIFEST.in because that's not used in the poetry build backend: https://python-poetry.org/docs/basic-usage/

.gitlab-ci.yml

@@ -4,10 +4,7 @@ pypi-release:
   rules:
     - if: '$CI_COMMIT_TAG =~ /^v\d+/'
   script:
-    - pip3 install --upgrade pip build twine check-manifest
     - rm -f dist/*
-    - python3 -m check_manifest
-    - python3 -m build
-    - python3 -m twine check dist/*
-    - TWINE_USERNAME=${PYPI_USER} TWINE_PASSWORD=${PYPI_PASSWORD} python3 -m twine upload --skip-existing --non-interactive dist/*
-
+    - uv build
+    - uvx twine check dist/*
+    - TWINE_USERNAME=${PYPI_USER} TWINE_PASSWORD=${PYPI_PASSWORD} uvx twine upload --skip-existing --non-interactive dist/*