chore: replace stale draft with canonical ts-TEMPLATE form for ts-homepage

- Replace alternate template form (with {{YOUR_TAILSCALE_AUTHKEY}}, sys_module
  cap, hardcoded homepage.damconsulting.net serve.json) with the canonical
  ts-TEMPLATE pattern: Tailscale sidecar + Homepage, both via network_mode
- Use named volume for config dir; default settings/services/bookmarks/widgets
  files included as starting points for the user to customize
- Add SECURITY.md and proper .gitignore (incl. Homepage's auto-generated
  custom.css/custom.js/docker.yaml/kubernetes.yaml/proxmox.yaml stubs +
  logs/)
- serve.headscale.json now uses the actual MagicDNS base domain
  (homepage.damconsulting.net) so the user has a working starting point
  to edit, not a {{service}} placeholder that doesn't resolve
- Verified: dashboard renders at homepage.damconsulting.net

.gitignore

@@ -4,3 +4,11 @@
 tskey-*
 authkey*
 tailscale/tailscale-data/
+homepage/images/
+homepage/config/logs/
+homepage/config/custom.css
+homepage/config/custom.js
+homepage/config/docker.yaml
+homepage/config/kubernetes.yaml
+homepage/config/proxmox.yaml
+