Restyle the Slides

## Do you have an eye for design?
Help us improve the look of the slide deck.
If you need help, check out the Appendix in the training manual.

The issue does not identify the slide-deck files, entry points, or specific visual changes. Start by locating the deck and reviewing the Appendix in the training manual; done should mean the slides have a consistently improved visual style, but the acceptance criteria are not defined.

由索引模型根据 Issue 内容生成。