Mark chapters as read without impacting reading speed

The proposed improvement for app is to add the functionality to manually mark individual chapters as read, even if the user hasn't fully read them. This feature allows readers to maintain a sense of progress in situations where they may have already covered certain sections or are revisiting a book. Importantly, this should not affect the reading speed metrics or progress calculations tracked by the app. The app would continue calculating the user's reading speed based solely on the chapters they have fully read, ensuring that the overall metrics remain accurate and unaffected by manual chapter markings.