feat: 选票自动生成报销明细并支持集中分类（08-29-reimbursement-expense-policy-invoice-guard）

server/prisma/schema.prisma

@@ -1497,7 +1497,7 @@ model ReimbursementForm {
 model ReimbursementItem {
   id               String   @id @default(uuid()) @db.Uuid
   reimbursement_id String   @db.Uuid
-  expense_type_id  String   @db.Uuid
+  expense_type_id  String?  @db.Uuid
   expense_date     DateTime @db.Date
   amount           Decimal  @db.Decimal(14, 2)
   description      String
@@ -1509,7 +1509,7 @@ model ReimbursementItem {
   updated_by String?  @db.Uuid
 
   reimbursement_form ReimbursementForm @relation(fields: [reimbursement_id], references: [id], onDelete: Cascade)
-  expense_type       ExpenseType       @relation(fields: [expense_type_id], references: [id], onDelete: Restrict)
+  expense_type       ExpenseType?      @relation(fields: [expense_type_id], references: [id], onDelete: Restrict)
 
   invoice_pool_items InvoicePool[]