Upgrade Babel runtime for optional chaining support

[evghenimelnic]

Summary

• switch the static client to Babel Standalone 7 via CDN so modern JSX/ESNext features compile correctly in the browser
• restore optional chaining usage in the notification card now that Babel handles it
• document the Babel runtime alongside the rest of the frontend stack in the README

Testing

• python -m compileall app

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https://chatgpt.com/codex/tasks/task_e_68e2dc54ec58832eac05775e82694a53

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

CORS defaults prevent the server from starting

The FastAPI app registers CORSMiddleware with allow_credentials=True but settings.allowed_origins defaults to ['*'] (see Settings.allowed_origins). Starlette raises ValueError: Cannot use allow_credentials=True with allow_origins=['*'] for this combination, so the application crashes on startup unless the environment variable is overridden. Provide explicit origins or disable credentials when using the wildcard to avoid a boot‑time failure.

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