style: update border-radius and padding values across components

- standardize border-radius from 8px to 6px for consistent styling
- adjust padding values from 1rem to 0.75rem for better visual hierarchy
- remove redundant overflow-y properties for cleaner code

docs/.vitepress/theme/components/appendix/llm-intro/LlmQuickStartDemo.vue

@@ -217,7 +217,7 @@ const scrollToBottom = () => {
 
 .messages {
   flex: 1;
-  overflow-y: auto;
+  
   padding: 20px;
   display: flex;
   flex-direction: column;