better item primary key and cart updates, balance updating WIP

prisma/schema.prisma

@@ -81,24 +81,27 @@ model Shop {
 }
 
 model Item {
-  item_name String @id
-  stock     Int
+  item_name String
   shopId    Int
+  stock     Int
 
   shop      Shop       @relation(fields: [shopId], references: [id], onDelete: Cascade, onUpdate: Cascade)
   sellables Sellable[]
+
+  @@id([item_name, shopId])
 }
 
 model Sellable {
   id        String  @id @default(cuid())
   item_name String
+  shopId    Int
   amount    Int
   price     Float
-  shopId    Int
   enabled   Boolean @default(true)
 
-  shop      Shop       @relation(fields: [shopId], references: [id], onDelete: Cascade, onUpdate: Cascade)
-  item      Item       @relation(fields: [item_name], references: [item_name], onDelete: Cascade, onUpdate: Cascade)
+  shop Shop @relation(fields: [shopId], references: [id], onDelete: Cascade)
+  item Item @relation(fields: [item_name, shopId], references: [item_name, shopId], onDelete: Cascade)
+
   cartItems CartItem[]
 }