feat: 添加布局顶部栏的登录和注册链接样式

frontend/portal/src/assets/layout/_topbar.scss

@@ -70,6 +70,19 @@
             color: var(--primary-contrast-color);
         }
 
+        &.layout-topbar-action-text {
+            width: auto;
+            height: auto;
+            border-radius: var(--content-border-radius);
+            padding: 0.25rem 0.75rem;
+            justify-content: flex-start;
+            gap: 0.5rem;
+
+            span {
+                display: inline;
+            }
+        }
+
         &.layout-topbar-user {
             width: auto;
             height: auto;

frontend/portal/src/layout/AppTopbar.vue

@@ -102,11 +102,11 @@ onMounted(() => {
                         <Menu ref="userMenuRef" :model="userMenuItems" popup />
                     </template>
                     <template v-else>
-                        <router-link to="/auth/login" class="layout-topbar-action">
+                        <router-link to="/auth/login" class="layout-topbar-action layout-topbar-action-text">
                             <i class="pi pi-sign-in"></i>
                             <span>登录</span>
                         </router-link>
-                        <router-link to="/auth/register" class="layout-topbar-action">
+                        <router-link to="/auth/register" class="layout-topbar-action layout-topbar-action-text">
                             <i class="pi pi-user-plus"></i>
                             <span>注册</span>
                         </router-link>