Add custom redirect handler for OIDC authentication

[EricWittmann]

Summary

• Adds optional onRedirect callback to OidcAuthOptions interface
• Enables custom client-side navigation after OIDC authentication
• Allows seamless integration with React Router and other routing libraries
• Maintains backwards compatibility by defaulting to window.location.href

Test plan

• Test OIDC authentication flow without custom redirect (should use default behavior)
• Test OIDC authentication with custom redirect handler (e.g., React Router's navigate)
• Verify state-based redirection still works correctly
• Verify stored location is properly retrieved and used for redirection

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