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/useAudioPlayer.ts

@@ -2,9 +2,12 @@ import type { Song } from '~/types/song'
 
 let audio: HTMLAudioElement | null = null
 let animationFrameId: number | null = null
+// Track which milestones have been fired for the current song
+const firedMilestones = new Set<number>()
 
 export function useAudioPlayer() {
   const store = usePlayerStore()
+  const { trackAudioPlay, trackAudioComplete, trackAudioProgress } = useTracking()
 
   function getAudio(): HTMLAudioElement {
     if (!audio) {
@@ -17,6 +20,10 @@ export function useAudioPlayer() {
       })
 
       audio.addEventListener('ended', () => {
+        if (store.currentSong) {
+          trackAudioComplete(store.currentSong.id, store.currentSong.title)
+        }
+        firedMilestones.clear()
         const next = store.nextSong()
         if (next) {
           loadAndPlay(next)
@@ -36,6 +43,16 @@ export function useAudioPlayer() {
     const update = () => {
       if (audio && !audio.paused) {
         store.setCurrentTime(audio.currentTime)
+        // Track progress milestones (25 / 50 / 75 %)
+        if (audio.duration > 0 && store.currentSong) {
+          const pct = (audio.currentTime / audio.duration) * 100
+          for (const milestone of [25, 50, 75] as const) {
+            if (pct >= milestone && !firedMilestones.has(milestone)) {
+              firedMilestones.add(milestone)
+              trackAudioProgress(store.currentSong.id, milestone)
+            }
+          }
+        }
       }
       animationFrameId = requestAnimationFrame(update)
     }
@@ -52,6 +69,7 @@ export function useAudioPlayer() {
   async function loadAndPlay(song: Song) {
     const el = getAudio()
     store.setSong(song)
+    firedMilestones.clear()
 
     // Try OGG first, fall back to MP3
     const oggPath = song.file.replace(/\.mp3$/, '.ogg')
@@ -64,6 +82,7 @@ export function useAudioPlayer() {
       await el.play()
       store.play()
       startTimeUpdate()
+      trackAudioPlay(song.id, song.title)
     }
     catch {
       // If OGG failed, try MP3
@@ -73,6 +92,7 @@ export function useAudioPlayer() {
           await el.play()
           store.play()
           startTimeUpdate()
+          trackAudioPlay(song.id, song.title)
         }
         catch (err) {
           console.error('Playback failed:', err)