Hold episode highlights until the episode is in the Spotify feed; auto-fill study lesson audio from the feed by season + episode; v2.19.0

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

server/routes/admin-content.js

@@ -1,3 +1,4 @@
+import { applyFeedRelease } from '../feed-release.js'
 import { mkdir, readFile } from 'node:fs/promises'
 import { writeFile } from '../atomic-write.js'
 import { assertPublicHttpsUrl } from '../url-safety.js'
@@ -249,7 +250,7 @@ export function register(app) {
     try {
       const parsed = await loadSiteContentFile(source === 'draft' ? DRAFT_DATA_FILE : DATA_FILE)
       if (source === 'published') {
-        const safeSiteContent = filterSiteContentByReleaseDate(parsed.siteContent)
+        const safeSiteContent = filterSiteContentByReleaseDate(await applyFeedRelease(parsed.siteContent))
         res.json({ ...parsed, siteContent: safeSiteContent })
         return
       }
@@ -279,7 +280,7 @@ export function register(app) {
   app.get('/api/site-config', async (_req, res) => {
     try {
       const parsed = await loadSiteContentFile(DATA_FILE)
-      const siteContent = parsed.siteContent ?? {}
+      const siteContent = await applyFeedRelease(parsed.siteContent ?? {})
       res.json({
         seo: siteContent.seo ?? DEFAULT_SEO,
         legal: siteContent.legal ?? DEFAULT_LEGAL,