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/backend-layered-architecture/ControllerLayerDemo.vue

@@ -250,7 +250,7 @@ const toggleDetails = (section) => {
   margin-top: 12px;
   padding: 16px;
   background: #f0f7ff;
-  border-radius: 8px;
+  border-radius: 6px;
   border-left: 4px solid #409eff;
 }
 
@@ -297,7 +297,7 @@ const toggleDetails = (section) => {
   text-align: center;
   padding: 16px 12px;
   background: #f8f9fa;
-  border-radius: 8px;
+  border-radius: 6px;
   transition: all 0.3s ease;
 }