refactor(layout-sider): 重构侧边栏布局结构并调整折叠模式

1.  将侧边栏折叠模式从transform改为width
2.  简化DOM层级，移除多余的sider-wrapper容器
3.  调整用户区定位使其固定在侧边栏底部
4.  优化图标渲染参数和菜单样式封装

src/layout/components/LayoutSider.vue

@@ -1,14 +1,13 @@
 <template>
   <n-layout-sider
     bordered
-    collapse-mode="transform"
+    collapse-mode="width"
     :collapsed-width="64"
     :width="240"
     :collapsed="layoutStore.siderCollapsed"
     :show-trigger="false"
     class="layout-sider"
   >
-    <div class="sider-wrapper">
     <!-- Logo -->
     <div class="sider-logo" @click="router.push('/dashboard')">
       <div class="logo-icon">
@@ -29,7 +28,6 @@
     </div>
 
     <!-- 菜单 -->
-      <div class="sider-menu">
     <n-menu
       :value="activeMenuKey"
       :collapsed="layoutStore.siderCollapsed"
@@ -39,7 +37,6 @@
       :default-expanded-keys="['system']"
       @update:value="onMenuSelect"
     />
-      </div>
 
     <!-- 用户区 -->
     <transition name="fade-text">
@@ -58,7 +55,6 @@
         </n-dropdown>
       </div>
     </transition>
-    </div>
   </n-layout-sider>
 </template>
 
@@ -93,7 +89,7 @@ const userInitial = computed(() => username.charAt(0).toUpperCase())
 
 // ─── Icon helper ───
 function renderIcon(icon: Component) {
-  return () => h(NIcon, { size: 18 }, { default: () => h(icon) })
+  return () => h(NIcon, null, { default: () => h(icon) })
 }
 
 function renderDropdownIcon(icon: Component) {
@@ -116,6 +112,7 @@ const menuOptions: MenuOption[] = [
   { key: 'plugin', label: '插件管理', icon: renderIcon(ExtensionPuzzleOutline), disabled: true },
   { key: 'settings', label: '系统设置', icon: renderIcon(SettingsOutline), disabled: true },
 ]
+
 const activeMenuKey = computed(() => route.path)
 
 function onMenuSelect(key: string) {
@@ -146,13 +143,6 @@ function onUserAction(key: string) {
   --n-sider-border-color: var(--color-border, #E5E6EB);
 }
 
-.sider-wrapper {
-  display: flex;
-  flex-direction: column;
-  height: 100%;
-  overflow: visible;
-}
-
 .sider-logo {
   display: flex;
   align-items: center;
@@ -179,27 +169,16 @@ function onUserAction(key: string) {
   white-space: nowrap;
 }
 
-.sider-menu {
-  flex: 1;
-  overflow: visible;
-  padding: 8px;
-  min-height: 0;
-}
-
-.sider-menu :deep(.n-menu) {
-  --n-item-height: 40px;
-  --n-border-radius: 6px;
-  --n-font-size: 14px;
-  --n-item-icon-size: 18px;
-}
-
 .sider-user {
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  right: 0;
   display: flex;
   align-items: center;
   gap: 8px;
   padding: 10px 14px;
   border-top: 1px solid var(--color-border, #E5E6EB);
-  flex-shrink: 0;
 }
 
 .user-meta {