Support React 19 as a peer dependency in ordercloud-react-sdk

[esitarz]

The SDK currently pins React 18 as a peer dependency, so consumers on React 19 can hit peer-dep mismatches.
Widen support to cover both 18 and 19.

Changes

• Update react/react-dom peer deps to ^18 || ^19.
• Bump @types/react / @types/react-dom to cover 19.
• Resolve any transitive peer-dep conflicts.

Acceptance Criteria

• Installs cleanly on React 18 and 19 with no peer warnings.
• Type-check/build passes against React 19.