feat(distribution): 分站可下调收号比例且不超过主站上限

让分销站能按自身能力下调收号比例扩大利润，同时把主站回收比例作为硬边界，避免分站把比例加得比主站更高。

Co-authored-by: Cursor <cursoragent@cursor.com>

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

@@ -49,6 +49,7 @@ const {
   priceConfig,
   fireLevelPlaceholder,
   dailyLossMAmount,
+  isDistribution,
   calculatedDefaultSaleRatio,
   maxAcceleratedSaleRatio,
   calculatedCoinBasePrice,
@@ -694,11 +695,16 @@ const screenshotGuides: Record<string, string> = {
         </p>
         <div class="ratio-panel">
           <div class="ratio-reference">
-            <span>参考比例</span>
+            <span>{{ isDistribution ? '主站收号上限' : '参考比例' }}</span>
             <strong>{{ calculatedDefaultSaleRatioText }}</strong>
           </div>
-          <p class="ratio-range">{{ saleRatioRangeText }}，比例越高出租速度越快，自行选择。</p>
-          <div class="ratio-mode-grid">
+          <p v-if="isDistribution" class="ratio-inherit-hint">
+            本站可下调收号比例换取更高利润，但不能高于主站比例。当前按站点配置计算。
+          </p>
+          <p class="ratio-range">
+            {{ saleRatioRangeText }}{{ isDistribution ? '。' : '，比例越高出租速度越快，自行选择。' }}
+          </p>
+          <div v-if="!isDistribution" class="ratio-mode-grid">
             <button
               type="button"
               class="ratio-mode-btn"