docs: Add SCIM provisioning documentation for Okta

[AvilaJulio]

Summary

• Convert the single Okta SSO page into a directory structure with separate SAML and SCIM guides, matching the Microsoft Entra ID documentation layout
• Add new SCIM provisioning guide covering: enabling SCIM in Cube Cloud, API key generation, Okta SCIM connection setup, provisioning actions (To App), user/group assignments, and pushing groups
• Include a warning about pre-existing user assignments before SCIM was enabled
• Add redirect from old /sso/okta URL to /sso/okta/saml

Test plan

• Verify /product/administration/sso/okta shows the index page with SAML/SCIM grid
• Verify /product/administration/sso/okta/saml renders the existing SAML guide
• Verify /product/administration/sso/okta/scim renders the new SCIM guide
• Verify the redirect from the old Okta URL works