style(RewardCategories): 调整奖励分类页面样式和图片

- 修改分类卡片高度为380rpx
- 更新健康分类和商户分类的图片URL
- 移除图片的objectPosition内联样式
- 调整商户分类的背景图定位为底部居中

 <!--
  * @Date: 2025-08-27 17:47:03
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-09-05 11:38:59
+ * @LastEditTime: 2025-09-05 13:48:14
  * @FilePath: /lls_program/src/pages/RewardCategories/index.vue
  * @Description: 文件描述
 -->
@@ -11,14 +11,14 @@
     <view class="flex-1 pb-20">
       <view class="p-4 space-y-4">
         <view v-for="(category, index) in categories" :key="category.id" class="rounded-lg overflow-hidden shadow-sm" @click="goToRewards(index)">
-            <view class="relative h-40">
+            <view class="relative" style="height: 380rpx;">
               <view class="absolute inset-0 bg-black bg-opacity-30 flex flex-col justify-end p-4 text-white">
                 <h3 class="text-xl font-bold mb-1">{{ category.title }}</h3>
                 <p class="text-sm text-white text-opacity-90">
                   {{ category.description }}
                 </p>
               </view>
-              <image mode="aspectFill" :src="category.image" :alt="category.title" class="w-full h-full object-cover" :style="{ objectPosition: category.bgPosition || 'center' }" />
+              <image mode="aspectFill" :src="category.image" :alt="category.title" class="w-full h-full object-cover" />
               <view v-if="category.iconUrl" class="absolute top-4 left-4 w-12 h-12 bg-white bg-opacity-90 rounded-full flex items-center justify-center">
                 <image :src="category.iconUrl" alt="" class="w-8 h-8" />
               </view>
@@ -40,14 +40,14 @@ const categories = ref([
     id: 'health',
     title: '银龄健康特色兑换区',
     description: '南京商圈线下实体店消费积分兑换',
-    image: "https://cdn.ipadbiz.cn/lls_prog/images/%E6%97%A0%E5%AD%97-%E7%A7%AF%E5%88%86%E5%95%86%E5%9F%8E.jpg",
+    image: "https://cdn.ipadbiz.cn/lls_prog/images/%E5%8D%97%E4%BA%AC%E8%B7%AF%E5%95%86%E5%9C%88.jpeg",
     bgPosition: 'center'
   },
   {
     id: 'online',
     title: '民政领域网上商城"银龄购"',
     description: '线上康复健康购物积分兑换',
-    image: 'https://images.unsplash.com/photo-1563013544-824ae1b704d3?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D&auto=format&fit=crop&w=1740&q=80',
+    image: 'https://cdn.ipadbiz.cn/lls_prog/images/%E6%97%A0%E5%AD%97-%E9%93%B6%E9%BE%84%E8%B4%AD.jpeg',
     bgPosition: 'center',
     bgColor: 'linear-gradient(135deg, #0ea5e9, #2563eb)',
   },
@@ -55,8 +55,8 @@ const categories = ref([
     id: 'merchants',
     title: '人驻商户多元场景广覆盖',
     description: '丰富商户积分兑换',
-    image: 'https://cdn.ipadbiz.cn/lls_prog/images/%E6%97%A0%E5%AD%97-%E9%93%B6%E9%BE%84%E8%B4%AD.jpeg',
-    bgPosition: 'center',
+    image: 'https://cdn.ipadbiz.cn/lls_prog/images/%E6%97%A0%E5%AD%97-%E7%A7%AF%E5%88%86%E5%95%86%E5%9F%8E.jpg',
+    bgPosition: 'bottom center',
     bgColor: 'linear-gradient(135deg, #007bff, #0056b3)',
   }
 ]);