fix(admin-web): 侧边栏菜单项过多时支持滚动，底部不再被截断

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/admin-web/src/components/layout/Sidebar/Sidebar.module.scss

@@ -122,10 +122,24 @@
   &__navWrapper {
     width: $sidebar-width;
     position: relative;
-    flex-shrink: 0;
     flex: 1;
+    min-height: 0;
     display: flex;
     flex-direction: column;
+    overflow-y: auto;
+    overflow-x: hidden;
+
+    /* 滚动条样式 */
+    &::-webkit-scrollbar {
+      width: 4px;
+    }
+    &::-webkit-scrollbar-track {
+      background: transparent;
+    }
+    &::-webkit-scrollbar-thumb {
+      background: rgba(255, 255, 255, 0.2);
+      border-radius: 2px;
+    }
   }
 
   &__nav {
@@ -133,11 +147,9 @@
     display: flex;
     flex-direction: column;
     align-items: flex-start;
-    justify-content: center;
     padding: 16px 4px 16px 16px;
     box-sizing: border-box;
     gap: 8px;
-    flex-shrink: 0;
   }
 
   &__toggle {