Use '.python-version' for builds

.github/workflows/build-container.yaml

@@ -22,11 +22,17 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Set build args
+        run: |
+          PYTHON_VERSION=$(cat .python-version)
+          echo "PYTHON_VERSION=$PYTHON_VERSION" >> $GITHUB_ENV
       - name: Build and push
         id: docker_build
         uses: docker/build-push-action@v6
         with:
           push: true
+          build-args: |
+            PYTHON_VERSION=${{ env.PYTHON_VERSION }}
           tags: |
             ghcr.io/${{ github.repository }}:${{ github.ref_name }}
             ghcr.io/${{ github.repository }}:latest

.github/workflows/release.yaml

@@ -14,8 +14,6 @@ jobs:
 
       - name: Setup Python
         uses: actions/setup-python@v5
-        with:
-          python-version: "3.9"
 
       - name: Install uv
         uses: astral-sh/setup-uv@v6