Add cross-site improvements across three phases

Phase 1 — Quick wins:
- Image lazy-loading on series/resource cards
- Newsletter signup added to Episodes page (before highlights)
- Per-route meta tags via usePageMeta hook (title, og:title, og:description)
- Breadcrumbs on study index, section, and notes pages
- SVG completion checkmark badges on study section list
- Analytics time-range filter (7d / 30d / 90d) in admin panel

Phase 2 — Medium features:
- Related episodes on archived series detail pages
- Resource library two-tier filter (type + tag chips)
- Global search (Fuse.js) moved below sticky header as full-width bar
- Q&A anonymous upvoting with localStorage dedup + admin pin/unpin
- Study enrollment funnel tracking (firstVisitAt, firstCompletionAt) with funnel chart in analytics

Phase 3 — Larger features:
- Study section comments (auto-approve for enrolled users, admin moderation panel)
- Study completion certificate (canvas render, PNG download, shareable public URL)
- Episode script full-text search (mammoth docx extraction, server-side search, admin upload UI)
- Reflection questions renamed from Discussion Questions; quiz answers can be shared to section discussion
- Public certificate route at /certificate/:token with og meta tags
- Comment moderation panel added to admin under Manage > Study Comments

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

server.js

@@ -13,6 +13,9 @@ import {
   loadStudyUsersFromDisk,
   loadStudyCommunityFromDisk,
   loadStudyRemindersFromDisk,
+  loadStudyCommentsFromDisk,
+  loadStudyCertificatesFromDisk,
+  loadEpisodeScriptsFromDisk,
   migrateStudyNotesIfNeeded,
   loadDownloadCountsFromDisk,
   loadPodcastChecklistFromDisk,
@@ -37,6 +40,9 @@ import { register as registerAdminAssets } from './server/routes/admin-assets.js
 import { register as registerStudyAuth } from './server/routes/study-auth.js'
 import { register as registerStudyData } from './server/routes/study-data.js'
 import { register as registerStudyAccount } from './server/routes/study-account.js'
+import { register as registerStudyComments } from './server/routes/study-comments.js'
+import { register as registerStudyCertificate } from './server/routes/study-certificate.js'
+import { register as registerEpisodeScripts } from './server/routes/episode-scripts.js'
 import { register as registerContact } from './server/routes/contact.js'
 import { register as registerQuestions } from './server/routes/questions.js'
 import { register as registerAnalytics } from './server/routes/analytics.js'
@@ -56,6 +62,9 @@ registerAdminAssets(app)
 registerStudyAuth(app)
 registerStudyData(app)
 registerStudyAccount(app)
+registerStudyComments(app)
+registerStudyCertificate(app)
+registerEpisodeScripts(app)
 registerContact(app)
 registerQuestions(app)
 registerAnalytics(app)
@@ -93,6 +102,9 @@ Promise.all([
   loadStudyUsersFromDisk(),
   loadStudyCommunityFromDisk(),
   loadStudyRemindersFromDisk(),
+  loadStudyCommentsFromDisk(),
+  loadStudyCertificatesFromDisk(),
+  loadEpisodeScriptsFromDisk(),
   migrateStudyNotesIfNeeded(),
   loadDownloadCountsFromDisk(),
   loadPodcastChecklistFromDisk(),