feat: 视频时长滑块支持最大 45 秒，适配广告视频多分镜场景

单次视频模型最高 15s，45s 总时长配 3 个分镜刚好每个 15s。
滑块 step 改为 5s，刻度标注 5/15/30/45 秒。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/features/ecommerce/panels/EcommerceClonePanel.tsx

@@ -666,15 +666,16 @@ export default function EcommerceClonePanel({
                   type="range"
                   min={cloneVideoDurationMin}
                   max={cloneVideoDurationMax}
-                  step={1}
+                  step={5}
                   value={cloneVideoDuration}
                   onChange={(event) => setCloneVideoDuration(clampCloneVideoDuration(Number(event.target.value)))}
                   aria-label="短视频时长"
                 />
                 <div className="clone-ai-duration-scale" aria-hidden="true">
                   <span>5秒</span>
-                  <span>10秒</span>
                   <span>15秒</span>
+                  <span>30秒</span>
+                  <span>45秒</span>
                 </div>
               </div>
             </div>