fix: Show skip/error reasons in car import results

- Backend: Include car_name in skipped response
- Frontend: Display skip details (car name + reason like "Already imported (ID: 123)")
- Frontend: Display error details with error message
- Add import process description during loading

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/carmodoo.py

@@ -1423,6 +1423,7 @@ async def import_cars_from_carmodoo(
                 skipped.append({
                     "car_no": car_data.car_no,
                     "car_id": existing.id,
+                    "car_name": car_data.car_name or existing.name or car_data.car_no,
                     "reason": "already exists"
                 })
                 continue