Add study user re-engagement reminder emails; v1.1.19

Sends 7/14/30-day inactivity emails to study users who haven't logged in,
with one-click HMAC-signed unsubscribe and automatic re-arm on next login.

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

server.js

@@ -29,13 +29,14 @@ import {
   refreshContentCaches,
   queueHitStatsWrite,
 } from './server/data.js'
-import { logResendEmailAlignmentWarnings, sendStudyReminderEmail } from './server/email.js'
+import { logResendEmailAlignmentWarnings, sendStudyReminderEmail, sendStudyReengagementEmail } from './server/email.js'
 import {
   detectBot,
   sanitizeUserAgent,
   shouldCountHit,
   recordHit,
   scheduleStudyReminders,
+  scheduleReengagementEmails,
 } from './server/study-helpers.js'
 import { recordVisitor } from './server/routes/analytics.js'
 
@@ -179,6 +180,14 @@ Promise.all([
     }, 60 * 60 * 1000)
     void scheduleStudyReminders(sendStudyReminderEmail)
 
+    // Send re-engagement emails to inactive study users every hour
+    setInterval(() => {
+      scheduleReengagementEmails(sendStudyReengagementEmail).catch(err => {
+        console.error('[study-reengagement] failed to schedule emails:', err)
+      })
+    }, 60 * 60 * 1000)
+    void scheduleReengagementEmails(sendStudyReengagementEmail)
+
     app.listen(PORT, () => {
       logResendEmailAlignmentWarnings()
       console.log(`Portfolio app listening on http://localhost:${PORT}`)