Remove obsolete project artifacts

prisma/schema.prisma

@@ -18,7 +18,6 @@ model Class {
   quizSets             QuizSet[]
   materialGroups       MaterialGroup[]
   spacedRepetitionSets SpacedRepetitionSet[]
-  arcadePacks          ArcadePack[]
 }
 
 model Deck {
@@ -150,52 +149,12 @@ model Setting {
 
 model StudyActivity {
   id         String   @id @default(uuid())
-  type       String // "FLASHCARD" | "QUIZ_QUESTION" | "ARCADE_GROUP"
+  type       String // "FLASHCARD" | "QUIZ_QUESTION"
   occurredAt DateTime @default(now())
 
   @@index([occurredAt])
 }
 
-model ArcadePack {
-  id                   String   @id @default(uuid())
-  classId              String
-  gameType             String
-  name                 String
-  description          String?
-  schemaVersion        Int
-  sourceJson           String
-  normalizedJson       String
-  validationReportJson String
-  sortOrder            Int      @default(0)
-  createdAt            DateTime @default(now())
-  updatedAt            DateTime @updatedAt
-
-  class    Class           @relation(fields: [classId], references: [id], onDelete: Cascade)
-  attempts ArcadeAttempt[]
-
-  @@index([classId, gameType, sortOrder])
-}
-
-model ArcadeAttempt {
-  id              String   @id @default(uuid())
-  arcadePackId    String
-  mode            String
-  score           Int
-  maxScore        Int
-  accuracy        Float
-  durationSeconds Int
-  mistakes        Int
-  hintsUsed       Int
-  settingsJson    String
-  resultsJson     String
-  seed            String
-  completedAt     DateTime @default(now())
-
-  arcadePack ArcadePack @relation(fields: [arcadePackId], references: [id], onDelete: Cascade)
-
-  @@index([arcadePackId, completedAt])
-}
-
 model MaterialGroup {
   id        String   @id @default(uuid())
   classId   String