Add Single File Demo (Sample)

Update utils.py

Change formula for multi-file proportion graph

Fix a bug with state change that can make index out of range

High x-axis tick value of time spoken graph

Fix Time Spoken chart

Update utils.py

revert to 20260408

Update utils.py

Re-order and rename the tabs, and adjust the content

Add new tab Rename Speaker

Added utils.py and state.py