fix: 卡片改为纯白底，图标和文字改为深色，简洁美观

src/pages/index/index.vue

@@ -7,7 +7,7 @@
         <text class="username">{{ userInfo.username || '用户' }}</text>
       </view>
       <view class="role-badge" :class="roleClass">
-        <Icon name="user" :size="24" color="#fff" />
+        <Icon name="user" :size="24" color="#667eea" />
         <text class="role-text">{{ roleText }}</text>
       </view>
     </view>
@@ -56,37 +56,37 @@
         <!-- 管理员菜单 -->
         <template v-if="isAdmin">
           <view class="menu-card" @click="goTo('/pages/order/create')">
-            <Icon name="edit" :size="36" color="#fff" />
+            <Icon name="edit" :size="36" color="#667eea" />
             <text class="menu-card-title">创建订单</text>
           </view>
           <view class="menu-card" @click="goToTab('/pages/order/list')">
-            <Icon name="order" :size="36" color="#fff" />
+            <Icon name="order" :size="36" color="#667eea" />
             <text class="menu-card-title">订单列表</text>
           </view>
           <view class="menu-card" @click="goTo('/pages/order/search')">
-            <Icon name="search" :size="36" color="#fff" />
+            <Icon name="search" :size="36" color="#667eea" />
             <text class="menu-card-title">订单查询</text>
           </view>
           <view class="menu-card" @click="goTo('/pages/order/return')">
-            <Icon name="right" :size="36" color="#fff" />
+            <Icon name="right" :size="36" color="#667eea" />
             <text class="menu-card-title">退货</text>
           </view>
         </template>
         <!-- 销售菜单 -->
         <template v-else-if="isSales">
           <view class="menu-card" @click="goTo('/pages/order/create')">
-            <Icon name="edit" :size="36" color="#fff" />
+            <Icon name="edit" :size="36" color="#667eea" />
             <text class="menu-card-title">创建订单</text>
           </view>
           <view class="menu-card" @click="goToTab('/pages/order/list')">
-            <Icon name="order" :size="36" color="#fff" />
+            <Icon name="order" :size="36" color="#667eea" />
             <text class="menu-card-title">订单列表</text>
           </view>
         </template>
         <!-- 顾客菜单 -->
         <template v-else-if="isCustomer">
           <view class="menu-card" @click="goToTab('/pages/order/list')">
-            <Icon name="order" :size="36" color="#fff" />
+            <Icon name="order" :size="36" color="#667eea" />
             <text class="menu-card-title">我的订单</text>
           </view>
         </template>
@@ -98,44 +98,44 @@
         <!-- 管理员菜单 -->
         <template v-if="isAdmin">
           <view class="menu-card" @click="goTo('/pages/product/manage')">
-            <Icon name="product" :size="36" color="#fff" />
+            <Icon name="product" :size="36" color="#667eea" />
             <text class="menu-card-title">商品管理</text>
           </view>
           <view class="menu-card" @click="goTo('/pages/category/index')">
-            <Icon name="setting" :size="36" color="#fff" />
+            <Icon name="setting" :size="36" color="#667eea" />
             <text class="menu-card-title">种类管理</text>
           </view>
           <view class="menu-card" @click="goStock()">
-            <Icon name="stock" :size="36" color="#fff" />
+            <Icon name="stock" :size="36" color="#667eea" />
             <text class="menu-card-title">库存管理</text>
           </view>
           <view class="menu-card" @click="goTo('/pages/stock/in')">
-            <Icon name="plus" :size="36" color="#fff" />
+            <Icon name="plus" :size="36" color="#667eea" />
             <text class="menu-card-title">入库</text>
           </view>
           <view class="menu-card" @click="goTo('/pages/stock/flow')">
-            <Icon name="flow" :size="36" color="#fff" />
+            <Icon name="flow" :size="36" color="#667eea" />
             <text class="menu-card-title">库存流水</text>
           </view>
         </template>
         <!-- 销售菜单 -->
         <template v-else-if="isSales">
           <view class="menu-card" @click="goTo('/pages/product/list')">
-            <Icon name="product" :size="36" color="#fff" />
+            <Icon name="product" :size="36" color="#667eea" />
             <text class="menu-card-title">商品浏览</text>
           </view>
         </template>
         <!-- 顾客菜单 -->
         <template v-else-if="isCustomer">
           <view class="menu-card" @click="goTo('/pages/product/list')">
-            <Icon name="product" :size="36" color="#fff" />
+            <Icon name="product" :size="36" color="#667eea" />
             <text class="menu-card-title">商品浏览</text>
           </view>
         </template>
         <!-- 游客菜单 -->
         <template v-else-if="isGuest">
           <view class="guest-card" @click="goTo('/pages/login/index')">
-            <Icon name="user" :size="80" color="#fff" />
+            <Icon name="user" :size="80" color="#667eea" />
             <text class="guest-text">点击登录</text>
           </view>
         </template>
@@ -167,7 +167,7 @@
     <!-- 退出登录 -->
     <view class="logout-section" v-if="!isGuest">
       <button class="logout-btn" @click="logout">
-        <Icon name="logout" :size="32" color="#fff" style="margin-right: 10rpx" />
+        <Icon name="logout" :size="32" color="#667eea" style="margin-right: 10rpx" />
         退出登录
       </button>
     </view>
@@ -424,7 +424,7 @@ export default {
 .menu-card {
   width: 18%;
   aspect-ratio: 1;
-  background: linear-gradient(135deg, #e0e5ec 0%, #ffffff 100%);
+  background: #ffffff;
   border-radius: 12rpx;
   margin: 8rpx;
   display: flex;
@@ -432,7 +432,7 @@ export default {
   align-items: center;
   justify-content: center;
   padding: 6rpx;
-  box-shadow: 0 4rpx 12rpx rgba(0, 0, 0, 0.08);
+  box-shadow: 0 2rpx 8rpx rgba(0, 0, 0, 0.06);
 }
 
 .menu-card:active {
@@ -441,7 +441,7 @@ export default {
 
 .menu-card-title {
   font-size: 20rpx;
-  color: #fff;
+  color: #333;
   font-weight: bold;
   margin-top: 6rpx;
 }
@@ -488,6 +488,7 @@ export default {
 }
 
 .menu-card-title {
+  color: #333;
   font-size: 28rpx;
   font-weight: bold;
   color: #333;