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-evolution/KubernetesDemo.vue

@@ -240,10 +240,10 @@ const resetCluster = () => {
 <style scoped>
 .container-docker-demo {
   border: 1px solid var(--vp-c-divider);
-  border-radius: 8px;
+  border-radius: 6px;
   background: var(--vp-c-bg-soft);
   padding: 1.5rem;
-  margin: 1rem 0;
+  margin: 0.5rem 0;
 }
 
 .demo-header {
@@ -273,8 +273,8 @@ const resetCluster = () => {
   flex: 1;
   background: var(--vp-c-bg);
   border: 2px solid var(--vp-c-divider);
-  border-radius: 8px;
-  padding: 1rem;
+  border-radius: 6px;
+  padding: 0.75rem;
   cursor: pointer;
   transition: all 0.3s;
 }
@@ -398,8 +398,8 @@ const resetCluster = () => {
 .benefit-card {
   background: var(--vp-c-bg);
   border: 1px solid var(--vp-c-divider);
-  border-radius: 8px;
-  padding: 1rem;
+  border-radius: 6px;
+  padding: 0.75rem;
   text-align: center;
   transition: all 0.2s;
 }