Fix uncleaned setTimeout in useTypingEffect hook

Refactor useTypingEffect to use a single useEffect with proper cleanup for all timers, preventing state updates on unmounted components.
Add unit tests to verify behavior and ensure no memory leaks on unmount.

package.json

@@ -24,10 +24,14 @@
     "react-router-dom": "^7.12.0"
   },
   "devDependencies": {
+    "@testing-library/dom": "^10.4.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "^19.2.9",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^5.1.2",
+    "jsdom": "^27.4.0",
     "typescript": "^5.9.3",
-    "vite": "^7.3.1"
+    "vite": "^7.3.1",
+    "vitest": "^4.0.17"
   }
 }