ux: Remove 'Generate frames' and trigger visualization on input

The current workflow requires the user to input an array and then scroll down to a separate "Generate frames" button. This is inefficient. The visualization should be triggered directly from the input area.

Proposed Solution (using Streamlit Forms):

Wrap the st.text_input for the array and a new "Visualize!" button inside an st.form.

When the user either clicks the "Visualize!" button OR presses Enter after typing in the input field, the form will be submitted, and the frame generation logic should run.

This will completely remove the need for the old, separate "Generate frames" button, making the UI much cleaner.