feat(paseo): add Go, Python, shell tooling, hostname and timezone

Go 1.26.8 from the official tarball and Python 3.12 via uv, since Debian
12 carries 1.19 and 3.11. Both land outside $HOME, which the paseo-home
volume would otherwise mask.

Hostname and timezone come from the environment rather than being fixed in
the compose file. Paseo uses the container hostname as the host label in
its web UI, so without one the UI shows a random container ID.

CLAUDE.md

@@ -11,6 +11,18 @@ shorter one. Existing services that still use `docker-compose.yml` stay as
 they are; do not rename them, not even while touching the file for something
 else.
 
+## Installing software in an image
+
+Follow the upstream project's own documented install method, or the one the
+community has settled on. In order of preference: the vendor's signed package
+repository, the vendor's official tarball or install script, then a well-known
+community installer. Do not hand-roll a download, and do not take a stale
+distro package just because `apt install` is shorter — check what version it
+actually gives you first.
+
+State the reason in a comment when the obvious route is the wrong one, so the
+next person does not "simplify" it back.
+
 The root `README.md` is an index only — it covers the shared conventions and
 links out to each service. Per-service detail (variables, ports, storage)
 belongs in that service's README, not the root one. Adding a service means