fix: 部门创建/更新时 parentId 空字符串导致外键约束违反

前端选择"无（根部门）"时传 parentId=""，空字符串是 falsy 跳过了
父部门存在性检查，但 ...data 展开后 Prisma 尝试创建 parentId=""
的部门，数据库外键约束违反（无 id="" 的部门）。

修复：创建/更新时将空字符串统一转为 null，并显式传字段而非展开。

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

backend/src/routes/department.routes.ts

@@ -36,16 +36,21 @@ router.get('/', authMiddleware, async (req: AuthRequest, res, next) => {
 router.post('/', authMiddleware, async (req: AuthRequest, res, next) => {
   try {
     const data = createDeptSchema.parse(req.body)
+    // 空字符串视为无父部门，统一转为 null
+    const parentId = data.parentId && data.parentId.trim() !== '' ? data.parentId : null
     let level = 0
-    if (data.parentId) {
-      const parent = await prisma.department.findFirst({ where: { id: data.parentId, orgId: req.user!.orgId! } })
+    if (parentId) {
+      const parent = await prisma.department.findFirst({ where: { id: parentId, orgId: req.user!.orgId! } })
       if (!parent) throw { code: 'NOT_FOUND', message: '父部门不存在' }
       level = parent.level + 1
     }
     const dept = await prisma.department.create({
       data: {
-        ...data,
+        name: data.name,
+        parentId,
         level,
+        sortOrder: data.sortOrder,
+        description: data.description,
         orgId: req.user!.orgId!,
         createdBy: req.user!.id,
       },
@@ -61,19 +66,27 @@ router.put('/:id', authMiddleware, async (req: AuthRequest, res, next) => {
   try {
     const { id } = req.params
     const data = updateDeptSchema.parse(req.body)
+    // 空字符串视为无父部门，统一转为 null
+    const parentId = data.parentId !== undefined && data.parentId !== null && data.parentId.trim() !== '' ? data.parentId : data.parentId === undefined ? undefined : null
     // 防止循环引用
-    if (data.parentId === id) throw { code: 'VALIDATION_ERROR', message: '不能将自身设为父部门' }
+    if (parentId === id) throw { code: 'VALIDATION_ERROR', message: '不能将自身设为父部门' }
     let level: number | undefined
-    if (data.parentId) {
-      const parent = await prisma.department.findFirst({ where: { id: data.parentId, orgId: req.user!.orgId! } })
+    if (parentId) {
+      const parent = await prisma.department.findFirst({ where: { id: parentId, orgId: req.user!.orgId! } })
       if (!parent) throw { code: 'NOT_FOUND', message: '父部门不存在' }
       level = parent.level + 1
-    } else if (data.parentId === null) {
+    } else if (parentId === null) {
       level = 0
     }
     const dept = await prisma.department.update({
       where: { id },
-      data: { ...data, level },
+      data: {
+        ...(data.name !== undefined ? { name: data.name } : {}),
+        ...(parentId !== undefined ? { parentId } : {}),
+        ...(data.sortOrder !== undefined ? { sortOrder: data.sortOrder } : {}),
+        ...(data.description !== undefined ? { description: data.description } : {}),
+        ...(level !== undefined ? { level } : {}),
+      },
     })
     res.json({ success: true, data: dept })
   } catch (err) {