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/lichen-markdown/upstream.md

@@ -0,0 +1,11 @@
+# Upstream
+
+## Images
+
+| Image | Source |
+|-------|--------|
+| `notplants/lichen-markdown` | [codeberg.org/ukrudt.net/lichen-markdown](https://codeberg.org/ukrudt.net/lichen-markdown) |
+
+## Release page
+
+https://codeberg.org/ukrudt.net/lichen-markdown/releases