调整文章标题输入框样式和提示文本

将 `q-input` 的 `label` 属性替换为 `placeholder` 属性，提示文本改为占位符形式。调整字体大小从 `23px` 增大到 `26px`，优化用户体验。

front/src/views/posts/write.vue

@@ -9,7 +9,7 @@
   <div class="text-h6" v-if="route.query.refer">复制来源ID：{{ route.query.refer }}</div>
   <!-- 文章标题 -->
   <div class="row">
-    <q-input autogrow class="col" v-model="post.Title" label="文章标题" outlined required :rules="[val => !!val || '请输入文章标题', val => val.length >= 2 || '标题至少2个字符', val => val.length <= 128 || '标题最多128个字符']" style="font-size: 23px;">
+    <q-input autogrow class="col" v-model="post.Title" placeholder="文章标题" outlined required :rules="[val => !!val || '请输入文章标题', val => val.length >= 2 || '标题至少2个字符', val => val.length <= 128 || '标题最多128个字符']" style="font-size: 26px;">
       <template v-slot:append>
         <q-btn dense size="lg" color="info" label="上传Word文档" @click="showWordUpload" class="full-width" icon="upload" no-caps />
       </template>