Add tsconfig.cy.json that extends the main tsconfig but removes the
rootDir restriction and adds Cypress types. Point ts-loader in
webpack.cy.config.ts to this dedicated tsconfig, fixing:
- TS6059: cypress/support files outside rootDir src/components
- TS2307: missing @storybook/react-webpack5 type declarations
- TS2339: toBeInTheDocument not found (jest-dom types scope)
