feat(channel): page details chaine multi-providers avec onglets et infinite scroll

- Strategy Pattern front: ChannelProviderInterface + 6 providers (yt/dm/tw/pt/od/ru) + factory (ids longs/courts)
- ChannelContentService: cache par onglet/tri/recherche (TTL 5min), pagination nextPage
- ChannelPage: header (banniere/avatar/subs/description ...plus), tabs dynamiques par capabilities, grilles videos/shorts 9:16/playlists/live, recherche debounced, tri recent/populaire, infinite scroll IntersectionObserver, skeletons/empty/error
- Backend: GET /api/channels/:provider/:id/content (videos/shorts/playlists/live) natif par provider

server/providers/youtube.mjs

@@ -20,6 +20,78 @@ function parseISODurationToSeconds(iso) {
   return (hours * 3600) + (minutes * 60) + seconds;
 }
 
+/**
+ * Resolve configured YouTube API keys.
+ * Accepts YOUTUBE_API_KEYS as JSON array ('["k1","k2"]') or CSV ('k1,k2'),
+ * plus the legacy single YOUTUBE_API_KEY as fallback. De-duplicated.
+ * @returns {string[]}
+ */
+function getYouTubeKeys() {
+  const keys = [];
+  try {
+    const raw = process.env.YOUTUBE_API_KEYS;
+    if (raw && String(raw).trim() && String(raw).trim() !== 'undefined' && String(raw).trim() !== 'null') {
+      const s = String(raw).trim();
+      if (s.startsWith('[')) {
+        try {
+          const arr = JSON.parse(s);
+          if (Array.isArray(arr)) keys.push(...arr.map(v => String(v || '').trim()).filter(Boolean));
+        } catch {}
+      } else {
+        keys.push(...s.split(',').map(v => String(v || '').trim()).filter(Boolean));
+      }
+    }
+  } catch {}
+  try {
+    const single = process.env.YOUTUBE_API_KEY;
+    if (single && String(single).trim()) keys.push(String(single).trim());
+  } catch {}
+  return Array.from(new Set(keys.filter(Boolean)));
+}
+
+/**
+ * Classify a YouTube API failure as retryable with another key.
+ * - 400 API_KEY_INVALID / "API key expired" -> key is dead, try next.
+ * - 403 quotaExceeded / rateLimitExceeded / dailyLimitExceeded -> quota, try next.
+ */
+function isKeyFailure(status, data) {
+  try {
+    const reason = data?.error?.errors?.[0]?.reason || '';
+    const message = String(data?.error?.message || '');
+    if (status === 400 && (reason === 'API_KEY_INVALID' || /api key (expired|invalid)/i.test(message))) return true;
+    if (status === 403 && /quota|rateLimit|dailyLimit|userRateLimit/i.test(reason + ' ' + message)) return true;
+  } catch {}
+  return false;
+}
+
+/** GET JSON from YouTube, rotating through keys on key failures. */
+async function ytFetchJson(base, paramsWithoutKey) {
+  const keys = getYouTubeKeys();
+  if (!keys.length) {
+    throw Object.assign(new Error('YOUTUBE_API_KEY not configured'), { ytStatus: 503, code: 'youtube_api_key_unavailable' });
+  }
+  let lastError = null;
+  let lastStatus = 500;
+  let lastData = null;
+  for (const key of keys) {
+    const params = new URLSearchParams(paramsWithoutKey);
+    params.set('key', key);
+    const resp = await fetch(`${base}?${params.toString()}`);
+    const data = await resp.json().catch(() => ({}));
+    if (resp.ok) return data;
+    lastStatus = resp.status;
+    lastData = data;
+    lastError = new Error(`YouTube API error: ${resp.status} ${data?.error?.message || ''}`.trim());
+    // Only rotate to the next key on key-attributable failures; otherwise fail fast.
+    if (!isKeyFailure(resp.status, data)) break;
+    console.warn(`[YouTube] key ...${String(key).slice(-4)} failed (${resp.status}), trying next key`);
+  }
+  const err = lastError || new Error(`YouTube API error: ${lastStatus}`);
+  err.ytStatus = lastStatus;
+  err.ytData = lastData;
+  throw err;
+}
+
 /** @type {{ id: 'yt', label: string, search: (q: string, opts: { limit: number, page?: number, sort?: 'relevance'|'date'|'views' }) => Promise<Suggestion[]> }} */
 const handler = {
   id: 'yt',
@@ -27,9 +99,9 @@ const handler = {
   async search(q, opts) {
     const { limit = 10, page = 1, sort = 'relevance' } = opts || {};
     try {
-      const API_KEY = process.env.YOUTUBE_API_KEY;
-      if (!API_KEY) {
-        throw new Error('YOUTUBE_API_KEY not configured');
+      const keys = getYouTubeKeys();
+      if (!keys.length) {
+        throw Object.assign(new Error('YOUTUBE_API_KEY not configured'), { ytStatus: 503, code: 'youtube_api_key_unavailable' });
       }
 
       let order = 'relevance';
@@ -44,21 +116,20 @@ const handler = {
       let lastItems = [];
 
       while (currentPage <= targetPage) {
-        const params = new URLSearchParams({
+        const params = {
           part: 'snippet',
           q: q,
           type: 'video',
           maxResults: String(perPage),
-          key: API_KEY,
-          order
-        });
-        if (pageToken) params.set('pageToken', pageToken);
+          order,
+          // Ne retourner que des vidéos lisibles en embed (évite l'erreur 153 côté player).
+          // Les vidéos non-embeddables sont filtrées via le champ status ci-dessous pour /videos.
+          videoEmbeddable: 'true',
+          safeSearch: 'moderate',
+        };
+        if (pageToken) params.pageToken = pageToken;
 
-        const response = await fetch(`https://www.googleapis.com/youtube/v3/search?` + params.toString());
-        if (!response.ok) {
-          throw new Error(`YouTube API error: ${response.status}`);
-        }
-        const data = await response.json();
+        const data = await ytFetchJson('https://www.googleapis.com/youtube/v3/search', params);
 
         if (currentPage === targetPage) {
           lastItems = Array.isArray(data.items) ? data.items : [];
@@ -82,18 +153,16 @@ const handler = {
 
       const detailsMap = new Map();
       if (videoIds.length > 0) {
-        const detailsParams = new URLSearchParams({
-          part: 'contentDetails,statistics',
-          id: videoIds.join(','),
-          key: API_KEY
-        });
-
-        const detailsResp = await fetch(`https://www.googleapis.com/youtube/v3/videos?${detailsParams.toString()}`);
-        if (detailsResp.ok) {
-          const detailsData = await detailsResp.json();
+        try {
+          const detailsData = await ytFetchJson('https://www.googleapis.com/youtube/v3/videos', {
+            part: 'contentDetails,statistics,status',
+            id: videoIds.join(','),
+          });
           for (const vid of detailsData?.items || []) {
             if (vid?.id) detailsMap.set(vid.id, vid);
           }
+        } catch (e) {
+          console.warn('[YouTube] details fetch failed, continuing without durations:', e?.message || e);
         }
       }
 
@@ -109,6 +178,10 @@ const handler = {
         const isoDuration = details?.contentDetails?.duration || '';
         const duration = parseISODurationToSeconds(isoDuration);
         const views = details?.statistics?.viewCount != null ? Number(details.statistics.viewCount) : undefined;
+        const channelId = snippet.channelId || undefined;
+        const channelHandle = snippet.channelTitle || undefined;
+        // status.embeddable === false -> le player renvoie l'erreur 153 ("Video configuration error").
+        const embeddable = details?.status ? details.status.embeddable !== false : undefined;
 
         return {
           title: snippet.title || '',
@@ -119,12 +192,20 @@ const handler = {
           type: 'video',
           duration: duration > 0 ? duration : undefined,
           views,
-          publishedAt: snippet.publishedAt || undefined
+          publishedAt: snippet.publishedAt || undefined,
+          channelId,
+          channelHandle,
+          channelExternalId: channelId,
+          channelUrl: channelId ? `https://www.youtube.com/channel/${channelId}` : undefined,
+          embeddable,
         };
       });
     } catch (error) {
-      console.error('YouTube search error:', error);
-      return [];
+      // Log explicite (clé expirée / quota) puis remonte l'erreur pour que
+      // /api/search la reporte dans `errors.yt` au lieu d'un groupe vide silencieux.
+      const status = error?.ytStatus || 500;
+      console.error(`YouTube search error (status ${status}):`, error?.message || error);
+      throw error;
     }
   }
 };