feat(admin): add restore dismissed alerts flow

Admins can now surface dismissed alert types without waiting for the
underlying data to change. Adds a collapsible "Restore dismissed"
section below the active alerts with per-type checkboxes.

- ALERT_METADATA map in adminAlerts.js as the single source of truth
  for slug → title/severity; detectors refactored to reference it
- GET /api/admin/alerts/dismissed returns this admin's dismissals
  joined with metadata (title, severity, dismissedAt)
- POST /api/admin/alerts/restore deletes dismissals by alertType[],
  returns the deleted count
- AdminAlertsPanel fetches both active + dismissed; stays visible
  when either is non-empty; checkboxes + "Restore selected" button
- adminAlertRestoreSchema validates the POST body against the enum
- Auth guards test covers both new routes

server/utils/adminAlerts.js

@@ -14,6 +14,25 @@ export const ALERT_THRESHOLDS = {
   NEAR_CAPACITY_RATIO: 0.8
 }
 
+// Single source of truth for alert presentation. Used by detectors AND the
+// dismissed-list endpoint (which has no access to a detector run's output).
+export const ALERT_METADATA = {
+  slack_invite_failed: { title: 'Slack invites failed', severity: 'critical' },
+  no_slack_handle_week: { title: 'Active members without a Slack handle', severity: 'attention' },
+  stuck_pending_payment: { title: 'Members stuck in pending payment', severity: 'attention' },
+  member_suspended: { title: 'Suspended members', severity: 'attention' },
+  preregistrant_selected_not_invited: { title: 'Pre-registrants selected but not invited', severity: 'attention' },
+  preregistrant_expired: { title: 'Expired pre-registrant invitations', severity: 'attention' },
+  event_draft_imminent: { title: 'Draft events with imminent start', severity: 'critical' },
+  event_near_capacity: { title: 'Events approaching capacity', severity: 'attention' },
+  tag_suggestions_pending: { title: 'Pending tag suggestions', severity: 'attention' }
+}
+
+function alertShell(type) {
+  const meta = ALERT_METADATA[type]
+  return { type, severity: meta.severity, title: meta.title }
+}
+
 const DAY_MS = 24 * 60 * 60 * 1000
 
 function daysAgo(days) {
@@ -50,9 +69,7 @@ export async function detectSlackInviteFailed() {
     .select('name email')
     .lean()
   return {
-    type: 'slack_invite_failed',
-    severity: 'critical',
-    title: 'Slack invites failed',
+    ...alertShell('slack_invite_failed'),
     items: members.map((m) => memberItem(m))
   }
 }
@@ -73,9 +90,7 @@ export async function detectNoSlackHandleAfterWeek() {
     .select('name email createdAt')
     .lean()
   return {
-    type: 'no_slack_handle_week',
-    severity: 'attention',
-    title: 'Active members without a Slack handle',
+    ...alertShell('no_slack_handle_week'),
     items: members.map((m) =>
       memberItem(m, `${daysSince(m.createdAt)} days since joining`)
     )
@@ -93,9 +108,7 @@ export async function detectStuckPendingPayment() {
     .select('name email createdAt')
     .lean()
   return {
-    type: 'stuck_pending_payment',
-    severity: 'attention',
-    title: 'Members stuck in pending payment',
+    ...alertShell('stuck_pending_payment'),
     items: members.map((m) =>
       memberItem(m, `${daysSince(m.createdAt)} days stuck`)
     )
@@ -109,9 +122,7 @@ export async function detectSuspendedMembers() {
     .select('name email')
     .lean()
   return {
-    type: 'member_suspended',
-    severity: 'attention',
-    title: 'Suspended members',
+    ...alertShell('member_suspended'),
     items: members.map((m) => memberItem(m))
   }
 }
@@ -136,9 +147,7 @@ export async function detectPreRegistrantSelectedNotInvited() {
     .select('name email updatedAt')
     .lean()
   return {
-    type: 'preregistrant_selected_not_invited',
-    severity: 'attention',
-    title: 'Pre-registrants selected but not invited',
+    ...alertShell('preregistrant_selected_not_invited'),
     items: preRegs.map((p) =>
       preRegItem(p, `${p.email} — ${daysSince(p.updatedAt)} days selected`)
     )
@@ -152,9 +161,7 @@ export async function detectPreRegistrantExpired() {
     .select('name email updatedAt')
     .lean()
   return {
-    type: 'preregistrant_expired',
-    severity: 'attention',
-    title: 'Expired pre-registrant invitations',
+    ...alertShell('preregistrant_expired'),
     items: preRegs.map((p) =>
       preRegItem(p, `${p.email} — expired ${daysSince(p.updatedAt)} days ago`)
     )
@@ -183,9 +190,7 @@ export async function detectDraftEventsImminent() {
     .select('title startDate')
     .lean()
   return {
-    type: 'event_draft_imminent',
-    severity: 'critical',
-    title: 'Draft events with imminent start',
+    ...alertShell('event_draft_imminent'),
     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`)
@@ -219,9 +224,7 @@ export async function detectEventsNearCapacity() {
     .filter(Boolean)
 
   return {
-    type: 'event_near_capacity',
-    severity: 'attention',
-    title: 'Events approaching capacity',
+    ...alertShell('event_near_capacity'),
     items: matched
   }
 }
@@ -234,16 +237,12 @@ export async function detectPendingTagSuggestions() {
     .lean()
   if (suggestions.length === 0) {
     return {
-      type: 'tag_suggestions_pending',
-      severity: 'attention',
-      title: 'Pending tag suggestions',
+      ...alertShell('tag_suggestions_pending'),
       items: []
     }
   }
   return {
-    type: 'tag_suggestions_pending',
-    severity: 'attention',
-    title: 'Pending tag suggestions',
+    ...alertShell('tag_suggestions_pending'),
     items: [
       {
         id: 'tag-suggestions',

server/utils/schemas.js

@@ -410,3 +410,10 @@ export const adminAlertDismissSchema = z.object({
   alertType: z.enum(ADMIN_ALERT_TYPES),
   signature: z.string().min(1).max(128)
 })
+
+export const adminAlertRestoreSchema = z.object({
+  alertTypes: z
+    .array(z.enum(ADMIN_ALERT_TYPES))
+    .min(1)
+    .max(ADMIN_ALERT_TYPES.length)
+})