feat: add Helm chart and release workflow

Adds a Helm chart under charts/hightower/ as an alternative to the
Flux/Kustomize deployment. Distributed via GitHub Pages (gh-pages branch).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

charts/hightower/.helmignore

@@ -0,0 +1,7 @@
+.DS_Store
+.git
+.gitignore
+.idea
+*.swp
+*.bak
+*.tmp