fix(WEB): SlatExtraInfo undefined 방어 처리

- length/slatCount/jointBar를 optional로 변경
- 값이 없거나 0인 경우 Badge 미표시

src/components/production/WorkerScreen/WorkItemCard.tsx

@@ -259,21 +259,27 @@ function SlatExtraInfo({
   slatCount,
   jointBar,
 }: {
-  length: number;
-  slatCount: number;
-  jointBar: number;
+  length?: number;
+  slatCount?: number;
+  jointBar?: number;
 }) {
   return (
     <div className="flex gap-2">
-      <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
-        길이 {formatNumber(length)}mm
-      </Badge>
-      <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
-        슬랫 매수 {slatCount}장
-      </Badge>
-      <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
-        조인트바 {jointBar}개
-      </Badge>
+      {length != null && length > 0 && (
+        <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
+          길이 {formatNumber(length)}mm
+        </Badge>
+      )}
+      {slatCount != null && slatCount > 0 && (
+        <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
+          슬랫 매수 {slatCount}장
+        </Badge>
+      )}
+      {jointBar != null && jointBar > 0 && (
+        <Badge variant="outline" className="text-xs px-2.5 py-1 border-gray-300">
+          조인트바 {jointBar}개
+        </Badge>
+      )}
     </div>
   );
 }