Add Amplify config and connection script, fix build path

[csecrestjr]

Summary

• add Amplify configuration with AppSync endpoint and API key
• provide a simple test script to verify frontend-to-backend connectivity
• guard the connection test with a DNS/TCP reachability check
• wire up npm script for running the connection test
• handle missing network connectivity gracefully in the test script
• track package-lock.json for reproducible frontend installs
• ensure Amplify build runs from the repo root using npm --prefix to avoid missing path errors

Testing

• npm install
• npm test
• npm run test-connection (warns: Network is unreachable. Skipping API call.)
• npm ci --prefix chat-ui
• npm run build --prefix chat-ui

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https://chatgpt.com/codex/tasks/task_e_68c4c875e9808321aa1d23569289cd36

[chatgpt-codex-connector]

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