style(PosterCheckin): 调整底部操作按钮的样式和层级

为底部操作按钮添加 z-index 确保显示层级，并统一按钮文字大小

@@ -97,16 +97,16 @@
       </view>
 
       <!-- 底部操作按钮 - 仅在正常状态显示 -->
-      <view v-if="pageState === 'normal'" class="bg-white border-t border-gray-200 p-4 safe-area-bottom" style="position: fixed; bottom: 0; left: 0; right: 0;">
+      <view v-if="pageState === 'normal'" class="bg-white border-t border-gray-200 p-4 safe-area-bottom z-50" style="position: fixed; bottom: 0; left: 0; right: 0;">
         <view class="flex gap-4">
           <view
-            class="flex-1 bg-gradient-to-r from-orange-400 to-orange-500 text-white py-3 px-6 rounded-lg font-medium shadow-lg active:scale-95 transition-transform duration-150 flex items-center justify-center gap-2"
+            class="flex-1 bg-gradient-to-r from-orange-400 to-orange-500 text-white text-sm py-3 px-6 rounded-lg font-medium shadow-lg active:scale-95 transition-transform duration-150 flex items-center justify-center gap-2"
             @click="chooseBackgroundImage"
           >
             <text>{{ currentPosterHasCustomBackground ? '更改照片' : '上传照片' }}</text>
           </view>
           <view
-            class="flex-1 text-white py-3 px-6 rounded-lg font-medium shadow-lg active:scale-95 transition-transform duration-150 flex items-center justify-center gap-2"
+            class="flex-1 text-white py-3 px-6 rounded-lg font-medium text-sm shadow-lg active:scale-95 transition-transform duration-150 flex items-center justify-center gap-2"
             :class="posterPath ? 'bg-gradient-to-r from-green-400 to-green-500' : (posterGenerateFailed ? 'bg-gradient-to-r from-orange-400 to-orange-500' : 'bg-gray-400')"
             @click="handlePosterAction"
             :disabled="!posterPath && !posterGenerateFailed"