Function render_centered_dialog 

pub fn render_centered_dialog(
    frame: &mut Frame<'_>,
    title: &str,
    border_color: Color,
    preferred_width: u16,
    lines: Vec<Line<'_>>,
)

Render a centered dialog overlay.

Computes a centered rectangle from preferred_width and the number of lines, clears the background, and draws a bordered paragraph.