Enhance video generation API: add polling URL, video URLs, and error handling; implement polling status endpoint with tests

Co-authored-by: Copilot <copilot@github.com>

backend/app/routers/generate.py

@@ -105,11 +105,15 @@ async def generate_video(
         raise HTTPException(
             status_code=status.HTTP_502_BAD_GATEWAY, detail=f"OpenRouter error: {exc}")
 
+    urls = result.get("unsigned_urls") or result.get("video_urls")
     return VideoResponse(
         id=result.get("id", ""),
-        model=result.get("model", body.model),
+        model=body.model,
         status=result.get("status", "queued"),
-        video_url=result.get("video_url"),
+        polling_url=result.get("polling_url"),
+        video_urls=urls,
+        video_url=(urls or [None])[0],
+        error=result.get("error"),
         metadata=result.get("metadata"),
     )
 
@@ -132,10 +136,39 @@ async def generate_video_from_image(
         raise HTTPException(
             status_code=status.HTTP_502_BAD_GATEWAY, detail=f"OpenRouter error: {exc}")
 
+    urls = result.get("unsigned_urls") or result.get("video_urls")
     return VideoResponse(
         id=result.get("id", ""),
-        model=result.get("model", body.model),
+        model=body.model,
         status=result.get("status", "queued"),
-        video_url=result.get("video_url"),
+        polling_url=result.get("polling_url"),
+        video_urls=urls,
+        video_url=(urls or [None])[0],
+        error=result.get("error"),
+        metadata=result.get("metadata"),
+    )
+
+
+@router.get("/video/status", response_model=VideoResponse)
+async def poll_video_status(
+    polling_url: str,
+    _: dict = Depends(get_current_user),
+) -> VideoResponse:
+    """Poll the status of a video generation job via its polling_url."""
+    try:
+        result = await openrouter.poll_video_status(polling_url)
+    except Exception as exc:
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY, detail=f"OpenRouter error: {exc}")
+
+    urls = result.get("unsigned_urls") or result.get("video_urls")
+    return VideoResponse(
+        id=result.get("id", ""),
+        model=result.get("model", ""),
+        status=result.get("status", "processing"),
+        polling_url=result.get("polling_url"),
+        video_urls=urls,
+        video_url=(urls or [None])[0],
+        error=result.get("error"),
         metadata=result.get("metadata"),
     )