fix: add EUR currency support

[anshitraj]

Summary

• add EUR to the shared Currency type
• allow EUR in payout and payin FX inputs
• type EUR payin responses correctly
• remove the resolved API-sync divergence and add a changeset

Closes #76.

Testing

• bun run check-types
• bun run lint:check
• bun run test -- src (100 passed)
• bun run build
• bun run contract-check
• bun run sync:check

[BernardoSM]

✅ Snyk checks have passed. No issues have been found so far.

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