fix: publish Helm chart to Gitea Package Registry instead of gh-pages

gh-pagesブランチへの独自index.yaml生成を廃止し、
helm-release.yamlと同じGitea Package Registry
(https://git.cafepieters.com/api/packages/helmchart/helm/)
への直接publishに統一。

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

.gitea/workflows/image-update-and-release.yaml

@@ -248,7 +248,7 @@ jobs:
             echo "Release v${APP_VERSION} created with asset ${PACKAGE_FILE}"
           fi
 
-      - name: Update Helm Repository Index
+      - name: Publish to Gitea Package Registry
         if: steps.check_update.outputs.wp_updated == 'true'
         run: |
           set -e
@@ -256,46 +256,15 @@ jobs:
           CHART_NAME=$(grep '^name:' Chart.yaml | awk '{print $2}')
           PACKAGE_FILE="${CHART_NAME}-${APP_VERSION}.tgz"
 
-          echo "Preparing Helm repository update..."
+          echo "🚀 Publishing ${PACKAGE_FILE} to Gitea Package Registry..."
 
-          # パッケージファイルを一時ディレクトリに移動
-          mkdir -p /tmp/helm-repo
-          cp "${PACKAGE_FILE}" /tmp/helm-repo/
+          curl --fail-with-body \
+            -u "${{ secrets.REGISTRY_USER }}:${{ secrets.REGISTRY_TOKEN }}" \
+            -X POST \
+            --upload-file "${PACKAGE_FILE}" \
+            "https://git.cafepieters.com/api/packages/helmchart/helm/api/charts"
 
-          # gh-pagesブランチの処理
-          if git ls-remote --heads origin gh-pages | grep gh-pages; then
-            echo "gh-pages branch exists, checking out..."
-            git fetch origin gh-pages
-            git checkout gh-pages
-          else
-            echo "Creating new gh-pages branch..."
-            git checkout --orphan gh-pages
-            git rm -rf . || true
-            echo "# Helm Repository" > README.md
-            git config user.name "Gitea Actions Bot"
-            git config user.email "actions@git.cafepieters.com"
-            git add README.md
-            git commit -m "Initialize gh-pages branch"
-            git push origin gh-pages
-          fi
-
-          # パッケージファイルをコピー
-          cp /tmp/helm-repo/"${PACKAGE_FILE}" .
-
-          # index.yamlを生成/更新
-          helm repo index . --url "https://git.cafepieters.com/${GITHUB_REPOSITORY}/raw/branch/gh-pages"
-
-          # コミットしてプッシュ
-          git config user.name "Gitea Actions Bot"
-          git config user.email "actions@git.cafepieters.com"
-          git add "${PACKAGE_FILE}" index.yaml
-          git commit -m "chore: add ${CHART_NAME} v${APP_VERSION}" || echo "No changes to commit"
-          git push origin gh-pages
-
-          echo "Helm repository updated successfully"
-
-          # mainブランチに戻る
-          git checkout main
+          echo "✅ Chart published successfully to Gitea Package Registry"
 
       - name: Summary
         if: always()