Test oidc sso example on ci

[lovasoa]

Add end-to-end Playwright tests for the OIDC SSO example to the CI workflow.

These tests validate the complete OIDC authentication flow, including happy paths, edge cases, and security-critical aspects like cookie attributes and nonce verification, ensuring the example functions correctly and securely.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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