Two concurrent series lanes, Complete studies, self-paced finished books; v2.9.0

- Study status 'complete' (manual or auto when all lessons released); stays enrollable and self-paced (no sequential lock, Resume button, Finished Studies hub section)
- Studies get lane (A/B) and expected start date; planned studies show "Starts <date>"; hub shows next lesson date instead of hardcoded pace
- Second concurrent series (homepage card, admin panel) with its own scheduled launch; transitions are per lane and flip the ending study to Complete and the incoming study to Active
- Finished books link to their study: "Study This Book" on playlist page, audio-only link from hub (playlist stays public, no account)
- Admin: bulk release scheduler (every N days), same-day collision warning, linked-study selects
- Weekly digest no longer dumps a finished study's backlog on late enrollees
- CI: build and tag the container as :beta on pushes to the beta branch

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

server/routes/study-certificate.js

@@ -16,7 +16,8 @@ const publicCertRateLimiter = rateLimit({
 })
 
 /**
- * Returns the list of required section IDs for a study (only released sections).
+ * 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
@@ -24,7 +25,7 @@ function getRequiredSectionIds(studySlug) {
   const study = content.studies.find(s => s?.slug === studySlug)
   if (!study || !Array.isArray(study.sections)) return null
   return study.sections
-    .filter(s => s?.status !== 'unreleased' && s?.id)
+    .filter(s => s?.id)
     .map(s => s.id)
 }