fix: sửa lỗi hiển thị logo trên trang pdf

backend/prisma/schema.prisma

@@ -118,14 +118,18 @@ model JoinRequest {
 }
 
 model TourParticipant {
+  id          String          @id @default(uuid())
   tourId      String
-  userId      String
+  userId      String?
   role        ParticipantRole @default(MEMBER)
+  displayName String?
+  adultCount  Int             @default(1)
+  childCount  Int             @default(0)
 
   tour        Tour         @relation(fields: [tourId], references: [id], onDelete: Cascade)
-  user        User         @relation(fields: [userId], references: [id], onDelete: Cascade)
+  user        User?        @relation(fields: [userId], references: [id], onDelete: Cascade)
 
-  @@id([tourId, userId])
+  @@unique([tourId, userId])
 }
 
 model Leg {
@@ -162,6 +166,8 @@ model Location {
   expenses        Expense[]
   photos          Photo[]
   comments        Comment[]
+
+  createdAt       DateTime  @default(now())
 }
 
 model Expense {