feat: add FX Cloudron package (DevOps-Tools) [#640]

FX 0.9.48 ("poor man's function as a service") as the 13th package:
pre-compiled goreleaser release binary with sha256 pin on
cloudron/base:4.0.0. fx is a CLI with no user concept, so the package
is a workstation: pinned binary + persistent workspace
(functions/ssh/kube) driven from the Cloudron web terminal, with an
auth-proxied landing page as the only HTTP surface (httpAuth proxy).
Deploys target remote Docker hosts over key-based SSH or Kubernetes
via FX_KUBECONF. Build green; runtime smoke (landing page, workspace
seeding, fx -v) green. Docs gardened to 13 packages.

Ticket: https://projects.knownelement.com/issues/640

Package-Workspace/DevOps-Tools/fx/.env.example

@@ -0,0 +1,14 @@
+# FX Cloudron package — environment knobs
+#
+# Set via App -> Configure -> Environment; they are visible to fx when
+# run from the app's web terminal. Not secrets.
+
+# Default deploy target for fx up/list/down/image: <user>@<host> of a
+# Docker host reachable over SSH. Leave unset to pass --host per
+# command. The SSH key itself is a file, not env: put it in
+# /app/data/ssh/ and pass --ssh_key (fx authenticates with keys only).
+#FX_HOST=deploy@docker.example.com
+
+# Path to a kubeconfig for Kubernetes deploys (or pass -C per command).
+# /app/data/kube/config is the persistent home for it.
+#FX_KUBECONF=/app/data/kube/config