fix(providers): forward userId from the providers API to executeProviderRequest

Large-attachment prep now needs request.userId for presigned URLs and access
checks; the authenticated providers proxy has auth.userId but wasn't passing it,
so oversized attachments failed for logged-in callers. Forwarding it makes large
files work there and keeps the access check (verifyFileAccess) intact.

Author: waleedlatif1

apps/sim/app/api/providers/route.ts

@@ -202,6 +202,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       responseFormat,
       workflowId,
       workspaceId,
+      userId: auth.userId,
       stream,
       messages,
       environmentVariables,