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

homepage/config/widgets.yaml

@@ -0,0 +1,18 @@
+---
+# Homepage widgets: https://gethomepage.dev/configs/widgets/
+# Info widgets shown at the top of the dashboard.
+
+- search:
+    provider: custom
+    url: https://www.google.com/search
+
+- resources:
+    cpu: true
+    memory: true
+    disk: /
+
+- datetime:
+    format:
+      timeStyle: short
+      dateStyle: medium
+