refactor(deps): migrate react-dom from v18.2.0 to v19.2.4

[digital-wizard48]

Changes

Dependency version bumps

• react: ^18.2.0 → ^19.2.4 (peer dependency, must be upgraded together with react-dom)
• react-dom: ^18.2.0 → ^19.2.4
• @types/react: ^18.2.70 → ^19.0.0 (type definitions for React 19)
• @types/react-dom: ^18.2.7 → ^19.0.0 (type definitions for React 19)

Breaking change: JSX.Element removed from global namespace

React 19 removes the global JSX namespace (and thus JSX.Element). All usages in app/components/ui-lib.tsx have been replaced with React.ReactElement, which is the explicit equivalent and the recommended approach going forward:

• Popover.children prop: JSX.Element → React.ReactElement
• Popover.content prop: JSX.Element → React.ReactElement
• Card.children prop: JSX.Element[] → React.ReactElement[]
• ListItem.icon prop: JSX.Element → React.ReactElement

No changes needed for createRoot

The createRoot API imported from react-dom/client is unchanged in React 19 and continues to work as before.

Notes

• Run yarn after merging to install the updated packages.
• If other files in the project use JSX.Element (not shown here), they will also need the same JSX.Element → React.ReactElement substitution.
• React 19 also deprecates ReactDOM.render (the legacy root API), but this codebase already uses createRoot exclusively, so no migration is needed there.

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This PR was auto-generated by Gittensor upgrade bot using Claude AI

[digital-wizard48]

Closing this PR — CI checks are failing and automated fixes have been exhausted. Thank you for considering this contribution.