Replace speed control buttons with a dynamic slider

The current speed control uses fixed buttons (1x, 2x, 4x, 8x), which feels clunky and offers limited options. We should replace this with a slider for a smoother, more intuitive user experience.

Implementation Plan:

Remove the existing st.button elements for speed control.

Implement st.slider to allow the user to select a speed value. A good range might be from 1 (slowest) to 10 (fastest).

The value from the slider should dynamically control the time.sleep() duration in the animation loop. For example, time.sleep(1 / slider_value).

The change must be reflected instantly as the user moves the slider, without needing to regenerate the frames.