refactor: 调整默认头像规则，由基于性别的固定头像调整为基于昵称展示（背景颜色基于昵称计算随机）

src/views/dashboard/workplace/components/Welcome.vue

@@ -2,11 +2,9 @@
   <a-card class="card" :bordered="false">
     <a-row align="center" wrap :gutter="[{ xs: 0, sm: 14, md: 14, lg: 14, xl: 14, xxl: 14 }, 16]" class="content">
       <a-space size="medium">
-        <a-avatar :size="68">
-          <img :src="userStore.avatar" alt="avatar" />
-        </a-avatar>
+        <Avatar :src="userStore.avatar" :name="userStore.nickname" :size="68" />
         <div class="welcome">
-          <p class="hello">{{ goodTimeText() }}！{{ userStore.name }}</p>
+          <p class="hello">{{ goodTimeText() }}！{{ userStore.nickname }}</p>
           <p>北海虽赊，扶摇可接；东隅已逝，桑榆非晚。</p>
         </div>
       </a-space>