recipe-maintainer: public snapshot (secrets + deployment plans removed, single commit)

Sanitized single-commit public mirror of recipe-maintainer.
- Removed test-ssh/.testenv (live creds); added test-ssh/.testenv.example placeholders.
- Removed plans/ and planned-updates/ (deployment-planning docs) so no client/
  deployment domains appear in the public repo.
- All other secret stores were already gitignored.
- docs.coopcloud.tech retained as a submodule (public upstream).

recipe-info/n8n/upstream.md

@@ -0,0 +1,15 @@
+# n8n Upstream
+
+## Main Project
+
+- **Repository:** https://github.com/n8n-io/n8n
+- **Releases:** https://github.com/n8n-io/n8n/releases
+- **Website:** https://n8n.io
+- **Docs:** https://docs.n8n.io
+
+## Images
+
+| Service | Image | Release Notes |
+|---------|-------|---------------|
+| app | `n8nio/n8n` | https://github.com/n8n-io/n8n/releases |
+| db (optional) | `postgres` | https://www.postgresql.org/docs/release/ |