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/routes/study-data.js

@@ -154,6 +154,13 @@ export function register(app) {
 
     const progress = await loadUserProgress(user.id)
     const completedSectionIds = progress.byStudy[studySlug]?.completedSectionIds ?? []
+
+    // Record first visit timestamp on the user record (additive, never overwrite)
+    if (!user.firstVisitAt) {
+      user.firstVisitAt = new Date().toISOString()
+      queueStudyUsersWrite()
+    }
+
     res.json({ studySlug, completedSectionIds })
   })
 
@@ -181,6 +188,12 @@ export function register(app) {
     state.studyProgressCache.set(user.id, progress)
     queueUserProgressWrite(user.id)
 
+    // Record first completion timestamp on the user record (additive, never overwrite)
+    if (!user.firstCompletionAt) {
+      user.firstCompletionAt = new Date().toISOString()
+      queueStudyUsersWrite()
+    }
+
     res.json({ ok: true, studySlug, completedSectionIds: studyProgress.completedSectionIds })
   })