jest und playwright tests feritg korrigiert

tests/playwright_e2e/header.spec.ts

tests/playwright_e2e/indexTest.spec.ts

tests/playwright_e2e/userRoundtrip.spec.ts

unitTests/jest/Chat.test.tsx

unitTests/jest/Plotter.test.tsx

unitTests/jest/VideoSlider.test.tsx

unitTests/jest/easyTests/FormAndImage.test.tsx

unitTests/jest/easyTests/Header.test.tsx

unitTests/jest/easyTests/TextContent.test.tsx