[Task](heureka): Migrate to modern JSX transform

[ArtieReus]

Task Description

Update the heureka app's TypeScript configuration to use the modern JSX transform (react-jsx) and remove unnecessary React imports, following the pattern established in #1975.

Sub-tasks

• Change "jsx": "react" to "jsx": "react-jsx" in heureka tsconfig.json
• Remove import React from 'react' statements from files that don't explicitly use the React object
• Keep React imports only where React APIs are directly referenced (e.g., useState, useEffect)
• Run pnpm build to verify builds pass
• Run pnpm typecheck to verify type checks pass
• Run pnpm test to verify all tests pass
• Run pnpm lint to ensure linting passes

Related Issues

• Parent issue: [EPIC](apps): Migrate to Clean TypeScript ESLint Configuration #1565
• Reference PR: chore(template): migrate to vite-react-ts eslint config and modern jsx #1975

Additional Context

This migration enables the modern JSX transform introduced in React 17, which eliminates the need to import React in every file that uses JSX. The transform automatically imports the necessary functions from
react/jsx-runtime. This should be completed before migrating the greenhouse app.