feat(admin): add event alert detectors

server/utils/adminAlerts.js

@@ -161,4 +161,69 @@ export async function detectPreRegistrantExpired() {
   }
 }
 
+function eventItem(ev, sublabel) {
+  return {
+    id: String(ev._id),
+    label: ev.title,
+    sublabel,
+    href: '/admin/events'
+  }
+}
+
+export async function detectDraftEventsImminent() {
+  await connectDB()
+  const now = new Date()
+  const horizon = new Date(now.getTime() + ALERT_THRESHOLDS.DRAFT_IMMINENT_DAYS * DAY_MS)
+  const events = await Event
+    .find({
+      isVisible: false,
+      isCancelled: { $ne: true },
+      startDate: { $gte: now, $lte: horizon }
+    })
+    .select('title startDate')
+    .lean()
+  return {
+    type: 'event_draft_imminent',
+    severity: 'critical',
+    title: 'Draft events with imminent start',
+    items: events.map((ev) => {
+      const days = Math.max(0, Math.ceil((new Date(ev.startDate).getTime() - Date.now()) / DAY_MS))
+      return eventItem(ev, `Starts in ${days} days`)
+    })
+  }
+}
+
+export async function detectEventsNearCapacity() {
+  await connectDB()
+  const now = new Date()
+  const events = await Event
+    .find({
+      'tickets.enabled': true,
+      'tickets.capacity.total': { $gt: 0 },
+      isCancelled: { $ne: true },
+      startDate: { $gte: now }
+    })
+    .select('title startDate tickets registrations')
+    .lean()
+
+  const matched = events
+    .map((ev) => {
+      const total = ev.tickets?.capacity?.total
+      if (!total) return null
+      const reserved = ev.tickets?.capacity?.reserved || 0
+      const taken = (ev.registrations?.length || 0) + reserved
+      const ratio = taken / total
+      if (ratio < ALERT_THRESHOLDS.NEAR_CAPACITY_RATIO) return null
+      return eventItem(ev, `${taken} / ${total} seats taken`)
+    })
+    .filter(Boolean)
+
+  return {
+    type: 'event_near_capacity',
+    severity: 'attention',
+    title: 'Events approaching capacity',
+    items: matched
+  }
+}
+
 // Aggregator lands in task 8.