feat(channel): identite chaine partagee cliquable partout + logos fiabilises

- Nouveau app-channel-identity (avatar+nom -> /channel, fallback resolve /api/channels, initiales sinon)
- ProviderBadge: accepte les ids courts yt/dm/tw/pt/od/ru
- Search adapters yt/dm/pt/od: conservent channelExternalId/channelAvatarUrl (pt derive instance|channel)
- video-card/themes/watch/related/suggestions/subscriptions/channel-header uniformises sur l'identite partagee

src/app/search/adapters/dm.ts

@@ -22,6 +22,8 @@ export class DmAdapter implements ProviderAdapter<VideoItem> {
       thumbnailUrl: it.thumbnail,
       viewCount: undefined, // Dailymotion API does not provide view count in search results
       publishedAt: undefined, // Dailymotion API does not provide published date in search results
+      channelExternalId: it.channelId || undefined,
+      channelAvatarUrl: it.uploaderAvatar || undefined,
     }));
     return { items, total: Array.isArray(res?.groups?.dm) ? res.groups.dm.length : 0 };
   }