Add complaint details modal to new UI

[filiperochalopes]

Summary

• add a dedicated API helper and modern modal to show complaint details without leaving the V2 experience
• wire the results list to fetch and open the modal when the user clicks any of the returned outcomes and surface basic error handling
• modernize the shared context/state used by both UIs so the modal can show loading states while details are being fetched

Testing

• npm run test (fails: jest: not found in the current environment)

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Codex Task