Enhance Work Instruction and Production Plan Functionality

- Added automatic migration to include a new column `batch_use` in the `item_info` table, allowing for batch usage management.
- Implemented logic to prevent deletion of work instructions that are in progress or completed, ensuring data integrity.
- Enhanced the `getBomBaseQtyMap` function to return batch usage status for items, defaulting to 'Y' if not specified.
- Introduced warnings for overdue items and insufficient production time in the production plan management, allowing users to proceed with caution.

(TASK: ERP-node-074, ERP-node-075, ERP-node-076)

frontend/components/common/TimelineScheduler.tsx

@@ -300,8 +300,12 @@ export default function TimelineScheduler({
           laneMap.set(ev.id, 0);
           continue;
         }
-        const evStart = parseDate(ev.startDate).getTime();
-        const evEnd = parseDate(ev.endDate).getTime();
+        // 잘못된/누락 날짜 가드: NaN이면 lane 계산이 무너져 박스가 겹침.
+        // start 무효 → 0, end 무효 또는 start 미만 → start 로 보정 (end >= start 보장).
+        const sRaw = parseDate(ev.startDate).getTime();
+        const eRaw = parseDate(ev.endDate).getTime();
+        const evStart = Number.isFinite(sRaw) ? sRaw : 0;
+        const evEnd = Number.isFinite(eRaw) ? Math.max(eRaw, evStart) : evStart;
         let placed = false;
         for (let l = 0; l < lanes.length; l++) {
           if (evStart > lanes[l].endTime) {
@@ -337,7 +341,8 @@ export default function TimelineScheduler({
   // ── 가상 스크롤 (리소스 행) ──
   // 대량 리소스(수천~만 단위) 환경에서 보이는 행만 DOM 마운트하여 성능 확보
   const barHeight = 24;
-  const barGap = 2;
+  // 세로 스택 시 박스 간 간격 — 좁으면 라벨 숫자끼리 붙어 보임. 명확히 분리.
+  const barGap = 6;
   const getRowHeight = useCallback((idx: number) => {
     const res = resources[idx];
     if (!res) return rowHeight;