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).

.opencode/skills/sync-secrets/SKILL.md

@@ -0,0 +1,6 @@
+---
+name: sync-secrets
+description: Sync Docker secrets from the test server into recipe-info/testsecrets/
+---
+Read and follow the full instructions in `.claude/commands/sync-secrets.md`.
+The recipe name will be provided by the user or calling agent.