fix: use GITHUB_REF/GITHUB_OUTPUT in release workflow

Gitea Actions uses GitHub-compatible variable names, not GITEA_* variants.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -10,6 +10,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
         
       - name: Set up Python
         run: |
@@ -18,22 +20,38 @@ jobs:
           
       - name: Install build tools
         run: |
-          python3 -m pip install --upgrade pip
+          python3 -m venv .venv
-          python3 -m pip install build twine
+          .venv/bin/pip install --upgrade pip
+          .venv/bin/pip install build twine
           
       - name: Build package
-        run: python3 -m build
+        run: .venv/bin/python -m build
         
       - name: Extract version from tag
         id: get_version
         run: echo "VERSION=${GITHUB_REF#refs/tags/v}" >> $GITHUB_OUTPUT
+      - name: Generate changelog
+        id: changelog
+        run: |
+          PREV_TAG=$(git tag --sort=-version:refname | grep -v "^${GITHUB_REF#refs/tags/}$" | head -1)
+          if [ -n "$PREV_TAG" ]; then
+            CHANGELOG=$(git log --pretty=format:"- %s" "${PREV_TAG}..HEAD")
+          else
+            CHANGELOG="Initial release"
+          fi
+          # Write multiline to output
+          {
+            echo "CHANGELOG<<EOF"
+            echo "$CHANGELOG"
+            echo "EOF"
+          } >> $GITHUB_OUTPUT
 
       - name: Upload to Gitea PyPI registry
         env:
           TWINE_USERNAME: ${{ secrets.PYPI_USERNAME }}
           TWINE_PASSWORD: ${{ secrets.PYPI_TOKEN }}
         run: |
-          python3 -m twine upload --repository-url https://git.wrede.ca/api/packages/andreas/pypi dist/*
+          .venv/bin/python3 -m twine upload --repository-url https://git.wrede.ca/api/packages/andreas/pypi dist/*
 
       - name: Create release
         uses: actions/gitea-release-action@v1
@@ -42,4 +60,4 @@ jobs:
             dist/*.whl
             dist/*.tar.gz
           title: "Release ${{ steps.get_version.outputs.VERSION }}"
-          body: "Release version ${{ steps.get_version.outputs.VERSION }}"
+          body: "${{ steps.changelog.outputs.CHANGELOG }}"