feat: auto-create MemberLunchPick on attendee writes

Adds ensureLunchPickForAttendingMember helper called from confirm,
adminConfirm, and editAttendees attendee-creation paths. No-ops when
the program has no LunchEvent.

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

src/server/services/lunch-pick-sync.ts

@@ -0,0 +1,33 @@
+import type { Prisma, PrismaClient } from '@prisma/client'
+
+type PrismaLike = PrismaClient | Prisma.TransactionClient
+
+/**
+ * Ensure a MemberLunchPick row exists for the given AttendingMember.
+ * No-ops when the parent program has no LunchEvent.
+ * Idempotent — safe to call repeatedly.
+ */
+export async function ensureLunchPickForAttendingMember(
+  prisma: PrismaLike,
+  attendingMemberId: string,
+): Promise<void> {
+  const member = await prisma.attendingMember.findUnique({
+    where: { id: attendingMemberId },
+    select: {
+      id: true,
+      confirmation: { select: { project: { select: { programId: true } } } },
+      lunchPick: { select: { id: true } },
+    },
+  })
+  if (!member) return
+  if (member.lunchPick) return
+  const programId = member.confirmation.project.programId
+  const lunchEvent = await prisma.lunchEvent.findUnique({
+    where: { programId },
+    select: { id: true },
+  })
+  if (!lunchEvent) return
+  await prisma.memberLunchPick.create({
+    data: { attendingMemberId: member.id },
+  })
+}