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/de.json

@@ -6209,7 +6209,6 @@
   "This installation will:": "Diese Installation wird:",
   "This installer will:": "Dieses Installationsprogramm wird:",
   "This interface is configured but doesn't exist physically": "Diese Schnittstelle ist konfiguriert, aber physisch nicht vorhanden",
-  "This interface runs on the Proxmox node as root. Open proxmenux-oci.sh on the Proxmox host.": "Diese Schnittstelle läuft auf dem Proxmox-Knoten als root. Öffnen Sie proxmenux-oci.sh auf dem Proxmox-Host.",
   "This is IRREVERSIBLE.": "Das ist irreversibel.",
   "This is a destructive action": "Dies ist eine destruktive Aktion",
   "This is a simple configuration change": "Dies ist eine einfache Konfigurationsänderung",