Add cron endpoint for automatic round open/close scheduling

New /api/cron/round-scheduler endpoint that:
- Activates DRAFT rounds whose windowOpenAt has arrived
- Closes ACTIVE rounds whose windowCloseAt has passed
- Uses existing activateRound/closeRound from round-engine
- Protected by CRON_SECRET header like other cron endpoints

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

src/app/api/cron/round-scheduler/route.ts

@@ -0,0 +1,82 @@
+import { NextResponse } from 'next/server'
+import type { NextRequest } from 'next/server'
+import { prisma } from '@/lib/prisma'
+import { activateRound, closeRound } from '@/server/services/round-engine'
+
+export async function GET(request: NextRequest): Promise<NextResponse> {
+  const cronSecret = request.headers.get('x-cron-secret')
+
+  if (!cronSecret || cronSecret !== process.env.CRON_SECRET) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  try {
+    const now = new Date()
+    const results: Array<{ roundId: string; action: string; success: boolean; errors?: string[] }> = []
+
+    // Find a SUPER_ADMIN to use as the actor for audit logging
+    const systemActor = await prisma.user.findFirst({
+      where: { role: 'SUPER_ADMIN' },
+      select: { id: true },
+    })
+
+    if (!systemActor) {
+      return NextResponse.json({
+        ok: false,
+        error: 'No SUPER_ADMIN user found for system actions',
+      }, { status: 500 })
+    }
+
+    // 1. Activate DRAFT rounds whose windowOpenAt has arrived
+    const roundsToOpen = await prisma.round.findMany({
+      where: {
+        status: 'ROUND_DRAFT',
+        windowOpenAt: { lte: now },
+        competition: { status: { not: 'ARCHIVED' } },
+      },
+      select: { id: true, name: true },
+    })
+
+    for (const round of roundsToOpen) {
+      const result = await activateRound(round.id, systemActor.id, prisma)
+      results.push({
+        roundId: round.id,
+        action: `activate: ${round.name}`,
+        success: result.success,
+        errors: result.errors,
+      })
+    }
+
+    // 2. Close ACTIVE rounds whose windowCloseAt has passed
+    const roundsToClose = await prisma.round.findMany({
+      where: {
+        status: 'ROUND_ACTIVE',
+        windowCloseAt: { lte: now },
+      },
+      select: { id: true, name: true },
+    })
+
+    for (const round of roundsToClose) {
+      const result = await closeRound(round.id, systemActor.id, prisma)
+      results.push({
+        roundId: round.id,
+        action: `close: ${round.name}`,
+        success: result.success,
+        errors: result.errors,
+      })
+    }
+
+    return NextResponse.json({
+      ok: true,
+      processed: results.length,
+      results,
+      timestamp: now.toISOString(),
+    })
+  } catch (error) {
+    console.error('Cron round-scheduler failed:', error)
+    return NextResponse.json(
+      { error: 'Internal server error' },
+      { status: 500 }
+    )
+  }
+}