feat(finalist): re-invite-safe confirmation reset helper

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/server/services/finalist-enrollment.ts

@@ -0,0 +1,66 @@
+import type { CompetitionCategory, Prisma, PrismaClient } from '@prisma/client'
+import { signFinalistToken } from '@/lib/finalist-token'
+
+type TxClient = PrismaClient | Prisma.TransactionClient
+
+/**
+ * Re-invite-safe variant of createPendingConfirmation. If a confirmation row
+ * already exists for the project (projectId is @unique), reset any
+ * non-CONFIRMED row back to a fresh PENDING with a new token/deadline and
+ * clear stale attendee rows; report CONFIRMED rows as a no-op so callers can
+ * skip them. Returns the row id + token + deadline for the email step.
+ */
+export async function resetOrCreatePendingConfirmation(
+  prisma: TxClient,
+  args: { projectId: string; category: CompetitionCategory; windowHours: number },
+): Promise<{ id: string; token: string; deadline: Date; alreadyConfirmed: boolean }> {
+  const deadline = new Date(Date.now() + args.windowHours * 3_600_000)
+  const existing = await prisma.finalistConfirmation.findUnique({
+    where: { projectId: args.projectId },
+    select: { id: true, status: true },
+  })
+
+  if (existing?.status === 'CONFIRMED') {
+    return { id: existing.id, token: '', deadline, alreadyConfirmed: true }
+  }
+
+  if (existing) {
+    const token = signFinalistToken({
+      confirmationId: existing.id,
+      exp: Math.floor(deadline.getTime() / 1000),
+    })
+    // Clear any attendee rows from a prior cycle (cascade-deletes flight/visa/lunch).
+    await prisma.attendingMember.deleteMany({ where: { confirmationId: existing.id } })
+    await prisma.finalistConfirmation.update({
+      where: { id: existing.id },
+      data: {
+        category: args.category,
+        status: 'PENDING',
+        deadline,
+        token,
+        confirmedAt: null,
+        declinedAt: null,
+        declineReason: null,
+        expiredAt: null,
+      },
+    })
+    return { id: existing.id, token, deadline, alreadyConfirmed: false }
+  }
+
+  const id = `cmfc_${Math.random().toString(36).slice(2, 10)}_${Date.now().toString(36)}`
+  const token = signFinalistToken({
+    confirmationId: id,
+    exp: Math.floor(deadline.getTime() / 1000),
+  })
+  await prisma.finalistConfirmation.create({
+    data: {
+      id,
+      projectId: args.projectId,
+      category: args.category,
+      status: 'PENDING',
+      deadline,
+      token,
+    },
+  })
+  return { id, token, deadline, alreadyConfirmed: false }
+}