fix: 跟进记录日期选择器添加 value-format 避免 422 错误

el-date-picker 默认返回 Date 对象，JSON 序列化为 ISO 格式，
Pydantic date 字段不接受，需显式指定 value-format="YYYY-MM-DD"

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/views/desktop/MiniBusiness.vue

@@ -389,7 +389,7 @@ async function quickStatusChange(row: any, newStatus: string) {
         <!-- Add Log Form -->
         <div class="log-add">
           <div class="log-add-row">
-            <el-date-picker v-model="logForm.log_date" type="date" size="small" style="width:140px" />
+            <el-date-picker v-model="logForm.log_date" type="date" value-format="YYYY-MM-DD" size="small" style="width:140px" />
             <div class="log-method-chips">
               <button v-for="m in logMethods" :key="m" type="button" class="log-chip" :class="{ 'log-chip--active': logForm.method === m }" :style="logForm.method === m ? { background: logMethodColors[m], borderColor: logMethodColors[m], color: '#fff' } : {}" @click="logForm.method = m">{{ m }}</button>
             </div>