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/database-intro/DatabaseRelationDemo.vue

@@ -121,10 +121,10 @@ const filteredOrders = computed(() => {
 <style scoped>
 .relation-demo {
   border: 1px solid var(--vp-c-divider);
-  border-radius: 8px;
+  border-radius: 6px;
   background: var(--vp-c-bg-soft);
-  padding: 1rem;
-  margin: 1rem 0;
+  padding: 0.75rem;
+  margin: 0.5rem 0;
 }
 
 .demo-header {
@@ -173,7 +173,7 @@ const filteredOrders = computed(() => {
 
 .table-card {
   background: var(--vp-c-bg);
-  border-radius: 8px;
+  border-radius: 6px;
   overflow: hidden;
   border: 1px solid var(--vp-c-divider);
 }
@@ -199,7 +199,7 @@ const filteredOrders = computed(() => {
 
 .table-content {
   max-height: 280px;
-  overflow-y: auto;
+  
 }
 
 .table-row {