fix(api): convert grok assets url to base64 in image response

app/api/v1/image.py

@@ -14,6 +14,7 @@
 from app.services.grok.services.image import ImageGenerationService
 from app.services.grok.services.image_edit import ImageEditService
 from app.services.grok.services.model import ModelService
+from app.services.grok.utils.download import DownloadService
 from app.services.token import get_token_manager
 from app.core.exceptions import ValidationException, AppException, ErrorType
 from app.core.config import get_config
@@ -304,6 +305,28 @@ async def create_image(request: ImageGenerationRequest):
         )
 
     data = [{response_field: img} for img in result.data]
+    # 如果返回的是受保护的 assets.grok.com URL，则用生成请求使用的 token 下载并转换为 base64
+    if len(data) > 0 and response_field in ["b64_json", "base64"] and any("assets.grok.com" in item[response_field] for item in data):
+        dl = DownloadService()
+        try:
+            new_data = []
+            any_converted = False
+            for item in data:
+                url = item.get("url")
+                if isinstance(url, str) and "assets.grok.com" in url:
+                    try:
+                        data_uri = await dl.parse_b64(url, token, "image")
+                        b64 = data_uri.split(",", 1)[1] if "," in data_uri else data_uri
+                        new_data.append({"b64_json": b64})
+                        any_converted = True
+                    except Exception:
+                        new_data.append({"url": url})
+                else:
+                    new_data.append(item)
+            if any_converted:
+                data = new_data
+        finally:
+            await dl.close()
     usage = result.usage_override or {
         "total_tokens": 0,
         "input_tokens": 0,