fix: avoid err shadow in feishu close check

Use distinct variable names (writeErr, closeErr) to avoid
shadowing the outer err, so a deferred close failure is
still captured.

pkg/channels/feishu/feishu_64.go

@@ -1013,9 +1013,9 @@ func (c *FeishuChannel) storeResourceFile(
 		})
 		return ""
 	}
-	if err := out.Close(); err != nil {
+	if closeErr := out.Close(); closeErr != nil {
 		logger.ErrorCF("feishu", "Failed to close downloaded resource file", map[string]any{
-			"error": err.Error(),
+			"error": closeErr.Error(),
 		})
 		os.Remove(localPath)
 		return ""