fixed so the code compiles

prisma/schema.prisma

@@ -36,13 +36,14 @@ model User {
   googleId    String   @unique
   email       String   @unique
   displayName String
-  username    String?  @unique
+  username    String   @unique
   avatarUrl   String?
   createdAt   DateTime @default(now())
   updatedAt   DateTime @updatedAt
 
-  sessions         GameSession[]
+  sessions           GameSession[]
   leaderboardEntries LeaderboardEntry[]
+  matchResults       MatchResult[]
 }
 
 model Question {
@@ -103,3 +104,16 @@ model LeaderboardEntry {
 
   @@unique([userId, grade])
 }
+
+model MatchResult {
+  id          String   @id @default(cuid())
+  userId      String
+  grade       Grade
+  won         Boolean
+  eloChange   Int
+  eloAfter    Int
+  timeSpentMs Int?
+  playedAt    DateTime @default(now())
+
+  user User @relation(fields: [userId], references: [id])
+}