Add study account engagement features; v1.2.4

- Pause reminders: remindersPausedUntil field + scheduler skip + account UI with 7/14/30-day presets
- Email digest mode: reminderFrequency field (immediate/weekly) + weekly digest email + scheduler + account UI toggle
- Admin user list improvements: streak, reengagement, frequency, pause, per-study lesson progress
- Admin manual re-engagement: POST endpoint + tier selector button in admin panel
- Study bookmarks: bookmarkedSectionIds in progress file + POST/DELETE endpoints + toggle button in lesson UI
- Study completion certificate email: auto-sent on first certificate issuance
- Content fields for certificate and weekly digest email templates in admin

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

server/routes/admin-assets.js

@@ -9,6 +9,7 @@ import {
   readUploadsMetadata,
   writeUploadsMetadata,
   getUserNotesFilePath,
+  loadUserProgress,
   queueStudyUsersWrite,
 } from '../data.js'
 import {
@@ -16,7 +17,9 @@ import {
   getStudyCatalog,
   normalizeStudySlug,
   isEnrollableStudySlug,
+  makeUnsubUrl,
 } from '../study-helpers.js'
+import { sendStudyReengagementEmail } from '../email.js'
 
 export function register(app) {
   app.get('/api/admin-assets', requireAdminAuth, async (_req, res) => {
@@ -117,9 +120,19 @@ export function register(app) {
         noteCount = Object.values(notes).filter(n => typeof n === 'string' && n.trim()).length
       } catch { /* ignore */ }
 
+      let progressByStudy = {}
+      try {
+        const prog = await loadUserProgress(user.id)
+        for (const [slug, data] of Object.entries(prog.byStudy)) {
+          progressByStudy[slug] = { completedLessons: (data.completedSectionIds ?? []).length }
+        }
+      } catch { /* ignore */ }
+
       const enrolledStudies = (user.enrolledStudySlugs ?? []).map(slug => {
         const study = catalog.find(s => s.slug === slug)
-        return study ? { slug, title: study.title } : { slug, title: slug }
+        return study
+          ? { slug, title: study.title, completedLessons: progressByStudy[slug]?.completedLessons ?? 0 }
+          : { slug, title: slug, completedLessons: 0 }
       })
 
       return {
@@ -132,12 +145,50 @@ export function register(app) {
         noteCount,
         subscribeNewsletter: user.subscribeNewsletter !== false,
         studyRemindersEnabled: user.studyRemindersEnabled === true,
+        reminderFrequency: user.reminderFrequency ?? 'immediate',
+        remindersPausedUntil: user.remindersPausedUntil ?? null,
+        currentStreak: user.currentStreak ?? 0,
+        longestStreak: user.longestStreak ?? 0,
+        reengagementSentAt: user.reengagementSentAt ?? {},
       }
     }))
 
     res.json({ users })
   })
 
+  app.post('/api/admin/study-users/:id/send-reengagement', requireAdminAuth, async (req, res) => {
+    const user = state.studyUsers.find(u => u.id === req.params.id)
+    if (!user) { res.status(404).json({ message: 'User not found.' }); return }
+
+    const tier = req.body?.tier
+    if (tier !== 't1' && tier !== 't2' && tier !== 't3') {
+      res.status(400).json({ message: 'tier must be t1, t2, or t3.' }); return
+    }
+
+    const studies = Array.isArray(state.cachedSiteContent?.studies) ? state.cachedSiteContent.studies : []
+    const enrolledStudySlugs = Array.isArray(user.enrolledStudySlugs) ? user.enrolledStudySlugs : []
+    const enrolledStudies = enrolledStudySlugs
+      .map(slug => studies.find(s => normalizeStudySlug(s?.slug) === slug))
+      .filter(Boolean)
+
+    if (enrolledStudies.length === 0) { res.status(400).json({ message: 'User has no enrolled studies.' }); return }
+
+    const firstStudy = enrolledStudies[0]
+    const studyTitle = enrolledStudies.length === 1 ? firstStudy.title : null
+    const canonical = state.cachedSiteContent?.seo?.canonicalUrl || 'https://versebyversewithnate.us/'
+    const base = canonical.endsWith('/') ? canonical.slice(0, -1) : canonical
+    const studyUrl = enrolledStudies.length === 1 ? `${base}/study/${firstStudy.slug}` : `${base}/study`
+    const unsubUrl = makeUnsubUrl(user.id)
+
+    try {
+      await sendStudyReengagementEmail(user.username, user.displayName || user.username, studyTitle, studyUrl, tier, unsubUrl)
+      res.json({ ok: true })
+    } catch (err) {
+      console.error(`[admin] manual reengagement send failed for ${user.username}:`, err)
+      res.status(500).json({ message: 'Failed to send email.' })
+    }
+  })
+
   app.patch('/api/admin/study-users/:id', requireAdminAuth, (req, res) => {
     const user = state.studyUsers.find(u => u.id === req.params.id)
     if (!user) { res.status(404).json({ message: 'User not found.' }); return }