fixed so the code compiles

prisma/migrations/20260526183414_username_required/migration.sql

@@ -0,0 +1,21 @@
+/*
+  Warnings:
+
+  - Made the column `username` on table `User` required. This step will fail if there are existing NULL values in that column.
+
+*/
+-- Backfill: assign a unique username derived from email or googleId for rows with NULL username
+UPDATE "User"
+SET "username" = lower(regexp_replace(split_part("email", '@', 1), '[^a-zA-Z0-9_]', '', 'g'))
+WHERE "username" IS NULL;
+
+-- Ensure uniqueness by appending a suffix for any collisions
+UPDATE "User" u
+SET "username" = u."username" || '_' || substr(u."id", 1, 6)
+WHERE (
+  SELECT COUNT(*) FROM "User" u2
+  WHERE u2."username" = u."username" AND u2."id" != u."id"
+) > 0;
+
+-- AlterTable
+ALTER TABLE "User" ALTER COLUMN "username" SET NOT NULL;

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])
+}