feat(WEB): 공정 단계 API 연동 - mock 데이터 제거

- actions.ts: 목데이터/스텁 함수를 실제 API 호출로 교체 (CRUD + reorder)
- actions.ts: ApiProcessStep 타입 + transformStepApiToFrontend 변환 추가
- actions.ts: ApiProcess에 steps 관계 매핑 추가
- ProcessListClient: 단계 수 workSteps → steps 기반으로 변경
- ProcessDetail: 드래그&드롭 후 reorder API 호출 추가

src/components/process-management/ProcessListClient.tsx

@@ -329,7 +329,7 @@ export default function ProcessListClient({ initialData = [], initialStats }: Pr
             <TableCell className="font-medium">{process.processCode}</TableCell>
             <TableCell>{process.processName}</TableCell>
             <TableCell>{process.department}</TableCell>
-            <TableCell className="text-center">{process.workSteps.length}</TableCell>
+            <TableCell className="text-center">{process.steps?.length ?? 0}</TableCell>
             <TableCell className="text-center">{itemCount > 0 ? itemCount : '-'}</TableCell>
             <TableCell className="text-center" onClick={(e) => e.stopPropagation()}>
               <Badge
@@ -383,7 +383,7 @@ export default function ProcessListClient({ initialData = [], initialStats }: Pr
             infoGrid={
               <div className="grid grid-cols-2 gap-x-4 gap-y-3">
                 <InfoField label="담당부서" value={process.department} />
-                <InfoField label="단계" value={`${process.workSteps.length}개`} />
+                <InfoField label="단계" value={`${process.steps?.length ?? 0}개`} />
                 <InfoField label="품목" value={itemCount > 0 ? `${itemCount}개` : '-'} />
               </div>
             }