feat: schema for lunch event, dishes, picks, externals

Adds LunchEvent (1:1 per Program), Dish, MemberLunchPick (1:1 per
AttendingMember), ExternalAttendee + DietaryTag/Allergen enums.
Allergens use the EU 14 regulated list.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prisma/schema.prisma

@@ -507,6 +507,7 @@ model Program {
   finalistSlotQuotas FinalistSlotQuota[]
   waitlistEntries    WaitlistEntry[]
   hotel              Hotel?
+  lunchEvent         LunchEvent?
 
   @@unique([name, year])
   @@index([status])
@@ -650,8 +651,9 @@ model Project {
   notificationLogs      NotificationLog[]
 
   // Grand-finale logistics
-  waitlistEntry        WaitlistEntry?
-  finalistConfirmation FinalistConfirmation?
+  waitlistEntry          WaitlistEntry?
+  finalistConfirmation   FinalistConfirmation?
+  externalLunchAttendees ExternalAttendee[]
 
   @@index([programId])
   @@index([status])
@@ -2731,6 +2733,7 @@ model AttendingMember {
   user            User                 @relation(fields: [userId], references: [id], onDelete: Cascade)
   flightDetail    FlightDetail?
   visaApplication VisaApplication?
+  lunchPick       MemberLunchPick?
 
   @@unique([confirmationId, userId])
   @@index([userId])
@@ -2809,3 +2812,110 @@ model VisaApplication {
 
   @@index([status])
 }
+
+// ─────────────────────────────────────────────────────────────────────────────
+// Grand-finale lunch event (PR 6)
+// Single configurable lunch event per edition. Each attending member has a
+// 1:1 MemberLunchPick (auto-created via lunch-pick-sync). External attendees
+// can be standalone or attached to a finalist project. Allergens use the
+// EU 14 regulated list; dishes carry dietary tags.
+// ─────────────────────────────────────────────────────────────────────────────
+
+enum DietaryTag {
+  VEGETARIAN
+  VEGAN
+  GLUTEN_FREE
+  PESCATARIAN
+}
+
+enum Allergen {
+  GLUTEN
+  CRUSTACEANS
+  EGGS
+  FISH
+  PEANUTS
+  SOYBEANS
+  MILK
+  TREE_NUTS
+  CELERY
+  MUSTARD
+  SESAME
+  SULPHITES
+  LUPIN
+  MOLLUSCS
+}
+
+model LunchEvent {
+  id                          String    @id @default(cuid())
+  programId                   String    @unique
+  enabled                     Boolean   @default(false)
+  eventAt                     DateTime?
+  endAt                       DateTime?
+  venue                       String?
+  notes                       String?   @db.Text
+  changeCutoffHours           Int       @default(48)
+  reminderHoursBeforeDeadline Int?
+  cronEnabled                 Boolean   @default(true)
+  extraRecipients             String[]  @default([])
+  reminderSentAt              DateTime?
+  recapSentAt                 DateTime?
+  createdAt                   DateTime  @default(now())
+  updatedAt                   DateTime  @updatedAt
+
+  program           Program            @relation(fields: [programId], references: [id], onDelete: Cascade)
+  dishes            Dish[]
+  externalAttendees ExternalAttendee[]
+}
+
+model Dish {
+  id           String       @id @default(cuid())
+  lunchEventId String
+  name         String
+  sortOrder    Int          @default(0)
+  dietaryTags  DietaryTag[]
+  createdAt    DateTime     @default(now())
+  updatedAt    DateTime     @updatedAt
+
+  lunchEvent  LunchEvent         @relation(fields: [lunchEventId], references: [id], onDelete: Cascade)
+  memberPicks MemberLunchPick[]
+  externals   ExternalAttendee[]
+
+  @@index([lunchEventId])
+}
+
+model MemberLunchPick {
+  id                String     @id @default(cuid())
+  attendingMemberId String     @unique
+  dishId            String?
+  allergens         Allergen[] @default([])
+  allergenOther     String?
+  pickedAt          DateTime?
+  createdAt         DateTime   @default(now())
+  updatedAt         DateTime   @updatedAt
+
+  attendingMember AttendingMember @relation(fields: [attendingMemberId], references: [id], onDelete: Cascade)
+  dish            Dish?           @relation(fields: [dishId], references: [id], onDelete: SetNull)
+
+  @@index([dishId])
+}
+
+model ExternalAttendee {
+  id            String     @id @default(cuid())
+  lunchEventId  String
+  projectId     String?
+  name          String
+  email         String?
+  roleNote      String?
+  dishId        String?
+  allergens     Allergen[] @default([])
+  allergenOther String?
+  createdAt     DateTime   @default(now())
+  updatedAt     DateTime   @updatedAt
+
+  lunchEvent LunchEvent @relation(fields: [lunchEventId], references: [id], onDelete: Cascade)
+  project    Project?   @relation(fields: [projectId], references: [id], onDelete: SetNull)
+  dish       Dish?      @relation(fields: [dishId], references: [id], onDelete: SetNull)
+
+  @@index([lunchEventId])
+  @@index([projectId])
+}