feat: add NetBox Cloudron package (Infrastructure) [#648]

Official-image wrapper of netboxcommunity/netbox v4.6.10
(netbox-docker 5.0.2, Granian), digest-pinned. OIDC via
python-social-auth wired to the platform provider; RQ worker
backgrounded behind a web-port gate; addon waits cover the 30s
upstream DB timeout. Full-stack verified: migrations, Granian,
worker, login page + SSO button. 16/~57.

Detail + verification: https://projects.knownelement.com/issues/648#note-4976

Package-Workspace/Infrastructure/netbox/.env.example

@@ -0,0 +1,11 @@
+# NetBox operator knobs (all optional; defaults shown)
+# Copy values into the Cloudron app's custom env config as needed.
+
+# Django TIME_ZONE (IANA name)
+NETBOX_TIME_ZONE=UTC
+
+# Granian web workers (default 4; lower on small installs)
+NETBOX_GRANIAN_WORKERS=4
+
+# Expose Prometheus metrics at /metrics
+NETBOX_METRICS_ENABLED=false