fix: Improve release process with proper error handling and retry logic

Enhance the release tag creation and Helm package push procedures:

Create Helm package improvements:
- Add retry logic for git push (up to 3 attempts)
- Rebase on failure to resolve conflicts
- Fail with exit 1 if push ultimately fails (was silently ignored)
- Log success message

Create release tag improvements:
- Check if tag already exists before creating (avoid duplicate creation)
- Add retry logic for tag push (up to 3 attempts)
- Fail with exit 1 if push ultimately fails (prevents silent failures)
- Suppress error output during retry to keep logs clean
- Better logging of tag creation and push success

These changes ensure that:
1. Failed releases don't go unnoticed (exit 1 instead of ignoring)
2. Transient network issues are handled gracefully (retry mechanism)
3. Duplicate tags are avoided
4. Release artifacts are reliably pushed to remote

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

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

@@ -315,7 +315,23 @@ jobs:
           # パッケージファイルをコミット
           git add ./packages/*.tgz ./packages/index.yaml
           git commit -m "chore: Add Helm package for version ${{ steps.increment.outputs.new_chart_version }}" || echo "No package changes to commit"
-          git push origin main || echo "Failed to push packages (this may be expected)"
+
+          # パッケージのプッシュをリトライ機構付きで実行
+          MAX_RETRIES=3
+          RETRY_COUNT=0
+          until git push origin main || [ $RETRY_COUNT -eq $MAX_RETRIES ]; do
+            RETRY_COUNT=$((RETRY_COUNT+1))
+            echo "Push failed, retrying ($RETRY_COUNT/$MAX_RETRIES)..."
+            sleep 5
+            git pull --rebase origin main
+          done
+
+          if [ $RETRY_COUNT -eq $MAX_RETRIES ]; then
+            echo "ERROR: Failed to push Helm packages after $MAX_RETRIES attempts"
+            exit 1
+          fi
+
+          echo "Successfully pushed Helm packages"
 
       - name: Create release tag
         if: steps.update_values.outputs.chart_version_update_needed == 'true'
@@ -323,6 +339,11 @@ jobs:
           # リリースタグを作成（Chart.yaml更新時のみ）
           TAG_NAME="v${{ steps.increment.outputs.new_chart_version }}"
 
+          # タグが既に存在するか確認
+          if git rev-parse "$TAG_NAME" >/dev/null 2>&1; then
+            echo "INFO: Tag $TAG_NAME already exists locally"
+          else
+            # タグメッセージを作成
             cat << EOF > /tmp/tag_msg.txt
           Release $TAG_NAME
 
@@ -331,10 +352,25 @@ jobs:
           EOF
 
             git tag -a "$TAG_NAME" -F /tmp/tag_msg.txt
-          if ! git push origin "$TAG_NAME"; then
-            echo "WARNING: Failed to push tag (may already exist or network issue)"
+            echo "Created tag: $TAG_NAME"
           fi
 
+          # タグをプッシュ（リトライ付き）
+          MAX_RETRIES=3
+          RETRY_COUNT=0
+          until git push origin "$TAG_NAME" 2>/dev/null || [ $RETRY_COUNT -eq $MAX_RETRIES ]; do
+            RETRY_COUNT=$((RETRY_COUNT+1))
+            echo "Tag push failed, retrying ($RETRY_COUNT/$MAX_RETRIES)..."
+            sleep 5
+          done
+
+          if [ $RETRY_COUNT -eq $MAX_RETRIES ]; then
+            echo "ERROR: Failed to push tag $TAG_NAME after $MAX_RETRIES attempts"
+            exit 1
+          fi
+
+          echo "Successfully pushed tag: $TAG_NAME"
+
       - name: Summary
         if: always()
         run: |