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/components/book/BookPlayer.vue

@@ -102,7 +102,7 @@
               <!-- Song disc -->
               <div v-if="currentSong" class="reader-song">
                 <div class="reader-disc" :class="{ spinning: playerStore.isPlaying }">
-                  <img src="/images/book-cover-spread.jpg" alt="" class="reader-disc-img" />
+                  <img src="/images/Couv-Economie-du-don.jpg" alt="" class="reader-disc-img" />
                   <div class="reader-disc-hole" />
                 </div>
                 <span class="reader-song-name">{{ currentSong.title }}</span>
@@ -138,6 +138,7 @@
 
 <script setup lang="ts">
 const { data: bpContent } = await usePageContent('book-player')
+const { trackPlayerOpen, trackPlayerChapter, trackPlayerMode } = useTracking()
 
 const COL_GAP = 80
 
@@ -167,6 +168,7 @@ const scrollPercent = ref(0)
 
 // When switching back to paginated, recalc pages
 watch(readingMode, async (mode) => {
+  trackPlayerMode(mode === 'scroll' ? 'scroll' : 'guided')
   if (mode === 'paginated') {
     await nextTick()
     await nextTick()
@@ -288,6 +290,7 @@ function goToTrack(idx: number) {
   // Play the song
   const song = tracks.value[idx]?.song
   if (song) {
+    trackPlayerChapter(song.id)
     _skipSongWatch = true
     audioPlayer.loadAndPlay(song)
   }
@@ -378,6 +381,7 @@ function onTouchEnd(e: TouchEvent) {
 watch(isOpen, async (open) => {
   if (open) {
     showSommaire.value = false
+    trackPlayerOpen()
     await initBookData()
     await nextTick()
     overlayRef.value?.focus()