支持在线时间跨天并优化发布与筛选体验

允许在线时段 end 早于 start 表示跨天，统一展示「次日」文案；修复移动端价格区间清空后被 sessionStorage 回写；优化 PC/移动端在线时间控件密度与通栏展示。

frontend/src/features/seller/views/SellerListingCreateView.vue

@@ -81,6 +81,7 @@ const {
   canAddScreenshot,
   getScreenshotLimitHint,
   isAllDayOnline,
+  onlineTimeRangeHint,
   selectAllDayOnline,
   handleOnlineStartChange,
   handleOnlineEndChange,
@@ -341,36 +342,45 @@ function selectDailyLoss(value: string | number) {
 
           <div class="field-row panel-field-row online-time-row">
             <label>在线时间<span>*</span></label>
-            <div class="online-time-controls">
-              <button
-                type="button"
-                class="time-chip"
-                :class="{ active: isAllDayOnline() }"
-                @click="selectAllDayOnline"
-              >
-                全天
-              </button>
-              <div class="online-time-range">
+            <div class="online-time-body">
+              <div class="online-time-controls">
+                <button
+                  type="button"
+                  class="time-chip"
+                  :class="{ active: isAllDayOnline() }"
+                  @click="selectAllDayOnline"
+                >
+                  全天
+                </button>
                 <el-time-picker
                   v-model="form.online_start"
                   value-format="HH:mm"
                   format="HH:mm"
                   placeholder="开始"
                   class="time-input"
+                  :clearable="false"
                   @change="handleOnlineStartChange"
                 />
                 <span class="online-time-sep">至</span>
+                <em v-if="onlineTimeRangeHint()" class="online-time-next-day">次日</em>
                 <el-time-picker
                   v-model="form.online_end"
                   value-format="HH:mm"
                   format="HH:mm"
                   placeholder="结束"
                   class="time-input"
+                  :class="{ 'is-cross': !!onlineTimeRangeHint() }"
+                  :clearable="false"
                   @change="handleOnlineEndChange"
                 />
               </div>
+              <p v-if="onlineTimeRangeHint()" class="online-time-summary">
+                {{ onlineTimeRangeHint() }}
+              </p>
+              <p class="field-hint">
+                请填写能稳定联系上您的时间，便于扫码、冻结人脸和订单交接。
+              </p>
             </div>
-            <p class="field-hint">请填写能稳定联系上您的时间，便于扫码、冻结人脸和订单交接。</p>
           </div>
 
           <div v-if="banRecordOptions.length" class="field-row panel-field-row">