refactor(oci): remove the shell entry point nothing runs

`oci/proxmenux-oci.sh` was installed on every Proxmox host and used on
none of them. The menu entry goes straight to the orchestrator:
scripts/oci/oci_manager_apps.sh runs `python3 -m proxmenux_oci` with
PYTHONPATH pointing at the engine.

Its only remaining caller was a message telling the reader to open it on
the Proxmox host — which is not how anyone gets in, and is what sent one
there to run it. That message now names the menu entry.

It could not be fetched and run either: it needs requirements.txt and
src/ beside it, so `wget | bash` resolved its own directory to the
working directory and failed on a path nobody chose. Making that work
would mean writing a second installer next to the one that already
ships the engine.

What it did offer was a virtualenv for a contributor generating the
catalog. The README now gives the direct invocation and names the two
distribution packages it needs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

lang/it.json

@@ -6209,7 +6209,6 @@
   "This installation will:": "Questa installazione:",
   "This installer will:": "Questo programma di installazione:",
   "This interface is configured but doesn't exist physically": "Questa interfaccia è configurata ma non esiste fisicamente",
-  "This interface runs on the Proxmox node as root. Open proxmenux-oci.sh on the Proxmox host.": "Questa interfaccia funziona sul nodo Proxmox come root. Aprire proxmenux-oci.sh sull'host Proxmox.",
   "This is IRREVERSIBLE.": "questo è IRREVERSIBILE.",
   "This is a destructive action": "Questa è un'azione distruttiva",
   "This is a simple configuration change": "Si tratta di una semplice modifica della configurazione",