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/config.js

@@ -33,6 +33,10 @@ export const UPLOADS_DIR = path.join(DATA_DIR, 'uploads')
 export const UPLOADS_META_FILE = path.join(DATA_DIR, 'uploads-meta.json')
 export const DOWNLOAD_COUNTS_FILE = path.join(DATA_DIR, 'download-counts.json')
 export const STUDY_REMINDERS_FILE = path.join(DATA_DIR, 'study-reminders.json')
+export const STUDY_COMMENTS_FILE = path.join(DATA_DIR, 'study-section-comments.json')
+export const STUDY_CERTIFICATES_FILE = path.join(DATA_DIR, 'study-certificates.json')
+export const EPISODE_SCRIPTS_FILE = path.join(DATA_DIR, 'episode-scripts.json')
+export const MAX_EPISODE_SCRIPT_LENGTH = 200_000 // ~150k words, well beyond any sermon
 
 export const DIST_DIR = path.join(ROOT_DIR, 'dist')
 export const INDEX_FILE = path.join(DIST_DIR, 'index.html')
@@ -60,6 +64,8 @@ export const CONTACT_EMAIL_COOLDOWN_MS = Math.max(10 * 1000, Number(process.env.
 export const DOWNLOAD_TOKEN_TTL_MS = 10 * 60 * 1000
 
 export const MAX_QUESTIONS = 1000
+export const MAX_STUDY_COMMENTS = 10000
+export const MAX_STUDY_COMMENT_LENGTH = 2000
 export const MAX_STUDY_USERS = 5000
 export const MAX_STUDY_ENROLLMENTS_PER_USER = 100
 export const MAX_STUDY_NOTES_PER_USER = 500