Add scheduled series auto-launch for series card, Start Here, and study guide; v2.0.36

One scheduled date/time in the Current Series admin panel archives the active series to
Finished Books and atomically swaps in new content for the series card, Start Here steps,
and Companion Study Guide. Server checks every hour via setInterval; also runs on restart
so the transition fires even if the server was down at the scheduled moment.

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

server.js

@@ -45,7 +45,7 @@ import { recordVisitor } from './server/routes/analytics.js'
 
 // Route registrars
 import { register as registerAdminAuth } from './server/routes/admin-auth.js'
-import { register as registerAdminContent } from './server/routes/admin-content.js'
+import { register as registerAdminContent, runScheduledSeriesTransition } from './server/routes/admin-content.js'
 import { register as registerAdminAssets } from './server/routes/admin-assets.js'
 import { register as registerAdminBackup } from './server/routes/admin-backup.js'
 import { register as registerStudyAuth } from './server/routes/study-auth.js'
@@ -209,6 +209,14 @@ Promise.all([
     }, 60 * 60 * 1000)
     void scheduleWeeklyDigestEmails(sendStudyWeeklyDigestEmail)
 
+    // Check for a scheduled series transition every hour
+    setInterval(() => {
+      runScheduledSeriesTransition().catch(err => {
+        console.error('[series-scheduler] error:', err)
+      })
+    }, 60 * 60 * 1000)
+    void runScheduledSeriesTransition()
+
     app.listen(PORT, () => {
       logResendEmailAlignmentWarnings()
       console.log(`Siteforge listening on http://localhost:${PORT}`)