feat: Overhaul chart UI with a modern look .

The current Matplotlib chart is standard. We want to transform it into something sleek, modern, and visually appealing.

Tasks:

Cleaner Look: Remove the top and right axis spines, the y-axis labels ("Value"), and the grid lines to create a minimalist feel.

Modern Colors: Instead of the default blue, use a cool color gradient for the bars. A gradient from a light teal to a deep blue would look great against the dark theme.

Dark Background: Give the chart itself a dark background color (e.g., #1E1E1E) to make it blend seamlessly with the app's theme.

Rounded Corners (Bonus): If possible with Matplotlib, adding slightly rounded corners to the bars would be a huge visual improvement.