website/integrations: add Icinga Web 2 (#22767)

* website/integrations: Icinga Web 2

Add an integration guide for Icinga Web 2 with OIDC SSO against
authentik via the third-party RISE-GmbH oidc module
(github.com/RISE-GmbH/icingaweb2-module-oidc). Covers the OAuth2/
OpenID Connect provider configuration in authentik (including the
module-specific redirect URI under /icingaweb2/oidc/authentication/
realm?name=<name>), the New Provider dialog in the Icinga Web 2 OIDC
module (Name, Url, Secret, Appname, Groups to sync, Enabled, Enforce
Https on redirect urls), an explicit hint to scope Groups to sync to
the few groups actually used for Icinga, and a pointer to assign
roles to the imported users and groups under Configuration >
Authentication > Roles. Tested with Icinga Web 2 2.13 and authentik
2026.5.2.

Also add Icinga to the integrations spell-check dictionary.

* website/integrations: Icinga Web 2: cleanup

Agent-thread: https://sdko.org/internal/threads/019e93e4-7da8-7432-81c3-dd7dca5f8590

A7k-product: product

A7k-product-repo: 2

Co-authored-by: Agent <agent@svc.sdko.net>

---------

Co-authored-by: nicedevil007 <nicedevil007@users.noreply.github.com>
Co-authored-by: Dominic R <dominic@goauthentik.io>
Co-authored-by: Agent <agent@svc.sdko.net>

locale/en/dictionaries/integrations.txt

@@ -25,6 +25,7 @@ Gravitee
 grommunio
 HACS
 Homarr
+Icinga
 Informatique
 Jellyseerr
 Kimai