fix: restore HOST override in zsh workspace services

Coolify injects HOST=0.0.0.0 and zsh's prompt reads $HOST instead of the
real hostname, so hostname: alone shows user@0. Set HOST=${SERVICE_HOSTNAME}
again in code-server, code-server-lsio and paseo.

paseo/.env.example

@@ -2,7 +2,8 @@
 #
 #   cp .env.example .env
 
-# Container hostname, shown as the host label in the web UI.
+# Container hostname, shown as the host label in the web UI. Also passed in as
+# HOST -- the name zsh's prompt shows.
 SERVICE_HOSTNAME=paseo
 
 # Password for the daemon API and web UI. Also the paseo user's login password,