fix(helm): trigger chart release workflow on helm chart tags

The helm-release workflow was only triggering on v* tags (MCP server
releases), not on nextcloud-mcp-server-* tags (helm chart releases).

This caused chart releases to be skipped because:
1. Helm chart version bump creates tag nextcloud-mcp-server-X.Y.Z
2. Workflow never runs for this tag (pattern didn't match)
3. Next v* tag triggers workflow at wrong commit (Chart.yaml not updated)
4. chart-releaser skips because version already exists

Fix: Add nextcloud-mcp-server-* to workflow trigger pattern so chart
releases execute at the correct commit where Chart.yaml has the new version.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/helm-release.yml

@@ -4,6 +4,7 @@ on:
   push:
     tags:
       - v*
+      - nextcloud-mcp-server-*
 
 jobs:
   release: