fix: complete admin input hints

src/modules/notifications/components/MessageComposerDialog.vue

@@ -68,7 +68,7 @@ async function submit() {
       <el-form-item label="消息模板" required><el-select v-model="form.templateCode" filterable placeholder="请选择已激活模板"><el-option v-for="item in templates" :key="item.id" :label="`${item.templateName}（${item.templateCode}）`" :value="item.templateCode" /></el-select></el-form-item>
       <div class="form-grid"><el-form-item label="接收对象" required><el-select v-model="form.recipientType"><el-option v-for="item in allowedRecipients" :key="item.value" :label="item.label" :value="item.value" /></el-select></el-form-item><el-form-item v-if="needsRole" label="角色编码" required><el-input v-model="form.roleCode" maxlength="64" placeholder="请输入服务端角色编码" /></el-form-item></div>
       <el-form-item v-if="needsIds" label="接收人用户 ID" required><el-input v-model="recipientIdsText" type="textarea" :rows="2" placeholder="多个用户 ID 使用逗号或换行分隔，最多 1000 个" /></el-form-item>
-      <section v-if="selectedTemplate?.variableWhitelist.length" class="variables"><strong>模板变量</strong><el-form-item v-for="key in selectedTemplate.variableWhitelist" :key="key" :label="key" required><el-input v-model="variables[key]" maxlength="2000" /></el-form-item></section>
+      <section v-if="selectedTemplate?.variableWhitelist.length" class="variables"><strong>模板变量</strong><el-form-item v-for="key in selectedTemplate.variableWhitelist" :key="key" :label="key" required><el-input v-model="variables[key]" maxlength="2000" placeholder="请输入变量值" /></el-form-item></section>
       <el-form-item label="定时发送"><div class="schedule-row"><el-switch v-model="scheduled" aria-label="启用定时发送" /><span>启用</span><el-date-picker v-model="form.scheduledAt" type="datetime" value-format="YYYY-MM-DDTHH:mm:ss" placeholder="选择发送时间" :disabled="!scheduled" /></div></el-form-item>
     </el-form>
     <template #footer="{ close }"><div class="dialog-actions"><el-button :disabled="submitting" @click="close">取消</el-button><el-button type="primary" :loading="submitting" @click="submit">{{ scheduled ? '确认定时发送' : '立即发送' }}</el-button></div></template>