ci: add python-version input to hynek action and UV_PYTHON env

- Pass python-version: '3.12' directly to hynek/build-and-inspect-python-package
  action to prevent it from defaulting to Python 3.x (which resolves to 3.14)
- Add UV_PYTHON: "3.12" env variable as additional safeguard for uv
- Keep actions/setup-python step for consistency

The hynek action has its own python-version input that defaults to 3.x,
which was overriding the runner's Python version set by actions/setup-python.
This comprehensive fix ensures Python 3.12 is used throughout the build process.

Co-Authored-By: AJ Steers <aj@airbyte.io>

Author: devin-ai-integration[bot]

.github/workflows/pypi_publish.yml

@@ -11,6 +11,8 @@ env:
 jobs:
   build:
     runs-on: ubuntu-latest
+    env:
+      UV_PYTHON: "3.12"
     steps:
     - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
       with:
@@ -19,6 +21,8 @@ jobs:
       with:
         python-version: '3.12'
     - uses: hynek/build-and-inspect-python-package@c52c3a4710070b50470d903818a7b25115dcd076 # v2.13.0
+      with:
+        python-version: '3.12'
 
   publish:
     name: Publish to PyPI