Completed studies: finishing a study keeps access after leaving; certificates always shown; no reminders for finished studies; v2.11.0

- Completion is stored on the user (completedStudySlugs, sticky) when every lesson is done; backfilled at startup
- Lessons, notes, progress, quiz, community and certificate stay open for completed studies after leaving the enrollment
- Dashboard/My Account list completed studies with Review Lessons and certificate access
- Study page shows a completed banner
- Lesson-release reminders, weekly digest and re-engagement emails skip finished studies
- Fix: streak fields (current/longest/last studied) and firstCompletionAt were dropped on every restart when users were loaded
- Tests for completion/access/re-engagement

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/routes/study-certificate.js

@@ -1,7 +1,7 @@
 import { randomUUID } from 'node:crypto'
 import rateLimit from 'express-rate-limit'
 import { requireAdminAuth } from '../auth.js'
-import { requireStudyAuth, normalizeStudySlug, isStudyUserEnrolled, getStudyTitleBySlug } from '../study-helpers.js'
+import { requireStudyAuth, normalizeStudySlug, hasStudyAccess, getStudyTitleBySlug, getRequiredSectionIds, markStudyCompletedIfDone } from '../study-helpers.js'
 import { state } from '../state.js'
 import { loadUserProgress, queueStudyCertificatesWrite } from '../data.js'
 import { sendStudyCertificateEmail, getCanonicalBaseUrl } from '../email.js'
@@ -15,20 +15,6 @@ const publicCertRateLimiter = rateLimit({
   message: { message: 'Too many certificate lookups. Please wait a moment.' },
 })
 
-/**
- * Returns the list of required section IDs for a study. Every lesson is required, so a
- * certificate is only available once the whole study has been released and completed.
- */
-function getRequiredSectionIds(studySlug) {
-  const content = state.cachedSiteContent
-  if (!content || !Array.isArray(content.studies)) return null
-  const study = content.studies.find(s => s?.slug === studySlug)
-  if (!study || !Array.isArray(study.sections)) return null
-  return study.sections
-    .filter(s => s?.id)
-    .map(s => s.id)
-}
-
 export function register(app) {
   // GET — check eligibility and return existing certificate token if one exists
   app.get('/api/study-certificate/:studySlug', requireStudyAuth, async (req, res) => {
@@ -36,7 +22,7 @@ export function register(app) {
     const studySlug = normalizeStudySlug(req.params.studySlug)
     if (!studySlug) { res.status(400).json({ message: 'Invalid study slug.' }); return }
 
-    if (!isStudyUserEnrolled(user, studySlug)) {
+    if (!hasStudyAccess(user, studySlug)) {
       res.status(403).json({ message: 'Not enrolled in this study.' }); return
     }
 
@@ -49,6 +35,8 @@ export function register(app) {
     const completedIds = progress.byStudy[studySlug]?.completedSectionIds ?? []
     const eligible = requiredIds.every(id => completedIds.includes(id))
 
+    if (eligible) markStudyCompletedIfDone(user, studySlug, completedIds)
+
     const existing = state.studyCertificates.find(c => c.userId === user.id && c.studySlug === studySlug)
 
     res.json({
@@ -67,7 +55,7 @@ export function register(app) {
     const studySlug = normalizeStudySlug(req.params.studySlug)
     if (!studySlug) { res.status(400).json({ message: 'Invalid study slug.' }); return }
 
-    if (!isStudyUserEnrolled(user, studySlug)) {
+    if (!hasStudyAccess(user, studySlug)) {
       res.status(403).json({ message: 'Not enrolled in this study.' }); return
     }