feat: SEO complet + analytics Umami + og:image § logo

SEO :
- composable useSeoPage() : og:*, Twitter Cards, canonical sur toutes les pages (15 pages)
- app.vue : JSON-LD Organization + Book, og:image global og-default.png
- og-default.png 1200×630 : logo § calligraphique + texte (Pillow)
- nuxt.config.ts : @nuxtjs/sitemap avec 26 URLs statiques

Analytics Umami :
- useTracking() : helpers typés audio/pdf/player/scroll/cta
- useScrollTracking() : scroll depth 25/50/75/100% + liens externes auto
- useAudioPlayer : trackAudioPlay/Progress/Complete
- BookPdfReader : trackPdfOpen/Close avec durée
- BookPlayer : trackPlayerOpen/Chapter/Mode
- docker-compose : variables NUXT_PUBLIC_UMAMI_* passées au container

Images :
- Couv-Economie-du-don.jpg ajoutée dans public/images/
- bookplayer.config.yml + home.yml : références mises à jour

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

app/composables/useTracking.ts

@@ -1,13 +1,19 @@
 /**
  * Umami analytics wrapper — safe server-side, no-op when not configured.
- * Usage: const { track } = useTracking()
- *        track('player:open')
- *        track('axis:navigate', { axis: 'numerique' })
+ *
+ * Events convention:
+ *   audio:play | audio:pause | audio:complete | audio:progress
+ *   pdf:open   | pdf:close
+ *   player:open | player:chapter | player:mode
+ *   scroll:depth
+ *   link:external
+ *   cta:click
  */
 export function useTracking() {
   const runtimeConfig = useRuntimeConfig()
   const enabled = !!runtimeConfig.public.umamiWebsiteId
 
+  // ── Core ────────────────────────────────────────────────────────────────
   function track(event: string, data?: Record<string, unknown>) {
     if (!import.meta.client || !enabled) return
     const umami = (window as Record<string, unknown>).umami as
@@ -16,5 +22,75 @@ export function useTracking() {
     umami?.track(event, data)
   }
 
-  return { track, enabled }
+  // ── Audio ────────────────────────────────────────────────────────────────
+  function trackAudioPlay(songId: string, songTitle: string, context?: string) {
+    track('audio:play', { song_id: songId, song_title: songTitle, context })
+  }
+
+  function trackAudioPause(songId: string, progressPct: number) {
+    track('audio:pause', { song_id: songId, progress_pct: progressPct })
+  }
+
+  function trackAudioComplete(songId: string, songTitle: string) {
+    track('audio:complete', { song_id: songId, song_title: songTitle })
+  }
+
+  /** Fired at 25 / 50 / 75 % milestones */
+  function trackAudioProgress(songId: string, milestone: 25 | 50 | 75) {
+    track('audio:progress', { song_id: songId, milestone })
+  }
+
+  // ── PDF ──────────────────────────────────────────────────────────────────
+  function trackPdfOpen(trigger?: string) {
+    track('pdf:open', { trigger })
+  }
+
+  function trackPdfClose(pagesVisited: number, durationMs: number) {
+    track('pdf:close', { pages_visited: pagesVisited, duration_ms: durationMs })
+  }
+
+  // ── BookPlayer ───────────────────────────────────────────────────────────
+  function trackPlayerOpen(trigger?: string) {
+    track('player:open', { trigger })
+  }
+
+  function trackPlayerChapter(chapterSlug: string) {
+    track('player:chapter', { chapter_slug: chapterSlug })
+  }
+
+  function trackPlayerMode(mode: 'guided' | 'scroll') {
+    track('player:mode', { mode })
+  }
+
+  // ── Navigation & UX ──────────────────────────────────────────────────────
+  function trackScrollDepth(page: string, depth: 25 | 50 | 75 | 100) {
+    track('scroll:depth', { page, depth })
+  }
+
+  function trackExternalLink(url: string, label?: string) {
+    const route = useRoute()
+    track('link:external', { url, label, from_page: route.path })
+  }
+
+  function trackCta(label: string, target?: string) {
+    const route = useRoute()
+    track('cta:click', { label, target, from_page: route.path })
+  }
+
+  return {
+    track,
+    enabled,
+    trackAudioPlay,
+    trackAudioPause,
+    trackAudioComplete,
+    trackAudioProgress,
+    trackPdfOpen,
+    trackPdfClose,
+    trackPlayerOpen,
+    trackPlayerChapter,
+    trackPlayerMode,
+    trackScrollDepth,
+    trackExternalLink,
+    trackCta,
+  }
 }