feat: Add SCIM + SSO JIT provisioning support for Entra ID

[Sanjai1994]

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feat: Add SCIM + SSO JIT provisioning support for Entra ID

• Fix NullPointerException in createSCIMUserAndAddToOrg endpoint
• Support placeholder user creation via SCIM for compliance
• Enable JIT provisioning on first SSO login with correct auth source
• Add comprehensive documentation for Entra ID integration
• Prevent auth source mismatch between SCIM and SSO authentication

This allows organizations to use SCIM for user pre-provisioning while maintaining proper SSO authentication with Entra ID (Azure AD).