feat: schema for finalist confirmation flow + per-category quotas

Adds 4 new models for grand-finale logistics PR 1:
- FinalistSlotQuota: per-category mutable quotas
- WaitlistEntry: ranked per-category waitlist
- FinalistConfirmation: token-gated confirmation lifecycle (PENDING /
  CONFIRMED / DECLINED / EXPIRED / SUPERSEDED) with optional decline reason
- AttendingMember: who from each team is attending, with visa flag

Plus Program.defaultAttendeeCap (default 3) for the per-edition team
attendance cap.

Migration is purely additive: no DROP/ALTER COLUMN/RENAME on existing
schema. All FKs ON DELETE CASCADE only fire on parent deletion.

prisma/schema.prisma

@@ -426,6 +426,9 @@ model User {
   // AI Ranking
   rankingSnapshots                  RankingSnapshot[]          @relation("TriggeredRankingSnapshots")
 
+  // Grand-finale logistics
+  finalistAttendances               AttendingMember[]
+
   @@index([role])
   @@index([status])
 }
@@ -483,6 +486,9 @@ model Program {
   description  String?
   settingsJson Json?         @db.JsonB
 
+  // Grand-finale logistics
+  defaultAttendeeCap Int @default(3) // Max team members allowed at the grand finale per finalist team
+
   createdAt DateTime @default(now())
   updatedAt DateTime @updatedAt
 
@@ -496,6 +502,10 @@ model Program {
   mentorMilestones  MentorMilestone[]
   competitions      Competition[]
 
+  // Grand-finale logistics
+  finalistSlotQuotas FinalistSlotQuota[]
+  waitlistEntries    WaitlistEntry[]
+
   @@unique([name, year])
   @@index([status])
 }
@@ -637,6 +647,10 @@ model Project {
   submissionPromotions  SubmissionPromotionEvent[]
   notificationLogs      NotificationLog[]
 
+  // Grand-finale logistics
+  waitlistEntry        WaitlistEntry?
+  finalistConfirmation FinalistConfirmation?
+
   @@index([programId])
   @@index([status])
   @@index([tags])
@@ -2626,3 +2640,89 @@ model ResultUnlockEvent {
   @@index([resultLockId])
   @@index([unlockedById])
 }
+
+// ─────────────────────────────────────────────────────────────────────────────
+// Grand-finale logistics (PR 1: finalist confirmation flow)
+// ─────────────────────────────────────────────────────────────────────────────
+
+enum WaitlistEntryStatus {
+  WAITING // available for promotion
+  PROMOTED // moved into a finalist slot
+  USED // promoted and confirmation flow completed (declined or accepted)
+}
+
+enum FinalistConfirmationStatus {
+  PENDING // sent, awaiting team response
+  CONFIRMED // team accepted, attendees selected
+  DECLINED // team explicitly declined
+  EXPIRED // deadline passed without response
+  SUPERSEDED // admin manually overrode (e.g. unconfirmed to allow quota decrease)
+}
+
+model FinalistSlotQuota {
+  id        String              @id @default(cuid())
+  programId String
+  category  CompetitionCategory
+  quota     Int
+  createdAt DateTime            @default(now())
+  updatedAt DateTime            @updatedAt
+
+  program Program @relation(fields: [programId], references: [id], onDelete: Cascade)
+
+  @@unique([programId, category])
+  @@index([programId])
+}
+
+model WaitlistEntry {
+  id        String              @id @default(cuid())
+  programId String
+  projectId String              @unique
+  category  CompetitionCategory
+  rank      Int
+  status    WaitlistEntryStatus @default(WAITING)
+  createdAt DateTime            @default(now())
+  updatedAt DateTime            @updatedAt
+
+  program Program @relation(fields: [programId], references: [id], onDelete: Cascade)
+  project Project @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  @@unique([programId, category, rank])
+  @@index([programId, category, status])
+}
+
+model FinalistConfirmation {
+  id                          String                     @id @default(cuid())
+  projectId                   String                     @unique
+  category                    CompetitionCategory
+  status                      FinalistConfirmationStatus @default(PENDING)
+  deadline                    DateTime
+  token                       String                     @unique
+  confirmedAt                 DateTime?
+  declinedAt                  DateTime?
+  declineReason               String? // optional free-text on decline
+  expiredAt                   DateTime?
+  promotedFromWaitlistEntryId String?                    @unique // null for original finalists
+  createdAt                   DateTime                   @default(now())
+  updatedAt                   DateTime                   @updatedAt
+
+  project          Project           @relation(fields: [projectId], references: [id], onDelete: Cascade)
+  attendingMembers AttendingMember[]
+
+  @@index([status, deadline]) // for cron scan
+  @@index([category, status])
+}
+
+model AttendingMember {
+  id             String   @id @default(cuid())
+  confirmationId String
+  userId         String // must be a TeamMember of the same project (validated at write time)
+  needsVisa      Boolean  @default(false)
+  createdAt      DateTime @default(now())
+  updatedAt      DateTime @updatedAt
+
+  confirmation FinalistConfirmation @relation(fields: [confirmationId], references: [id], onDelete: Cascade)
+  user         User                 @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@unique([confirmationId, userId])
+  @@index([userId])
+}