fix(ecommerce): video 400 error — use OSS URLs instead of data URLs for video generation

The renderScene function was passing local data URLs (data:image/png;base64,...)
as imageUrl and referenceUrls to createVideoTask, which the /api/ai/video endpoint
rejects with 400 Bad Request. The planning phase already uploads images to OSS
but the resulting URLs were not returned to the component.

- Add imageUrls field to EcommerceVideoPlanResult
- Return OSS imageUrls from runVideoPlan alongside existing plan data
- Use planResult.imageUrls[0] in handleRender instead of productImageDataUrls[0]
- Use planResult?.imageUrls[0] for sourceImage display fallback

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

src/features/ecommerce/ecommerceVideoService.ts

@@ -77,7 +77,7 @@ export async function runVideoPlan(
   const compliance = await checkCompliance(summary, selling, storyboard, signal);
   onStepDone("compliance");
 
-  return { summary, selling, creatives, storyboard, videoPrompts, compliance };
+  return { imageUrls, summary, selling, creatives, storyboard, videoPrompts, compliance };
 }
 
 export interface RenderSceneInput {