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/shared/components/channel-identity/channel-identity.component.html

@@ -0,0 +1,33 @@
+<a *ngIf="hasDestination; else plainBlock"
+   [routerLink]="['/channel', shortProvider, externalId]"
+   class="flex min-w-0 flex-1 items-center gap-2"
+   title="Ouvrir la page de la chaîne">
+  <span class="flex shrink-0 items-center justify-center overflow-hidden rounded-full border border-zinc-700 bg-zinc-800"
+        [class.h-6]="size === 'sm'" [class.w-6]="size === 'sm'"
+        [class.h-8]="size === 'md'" [class.w-8]="size === 'md'">
+    <img *ngIf="resolvedAvatar; else linkedInitials"
+         [src]="resolvedAvatar" [alt]="resolvedName" loading="lazy"
+         class="h-full w-full object-cover" referrerpolicy="no-referrer" />
+    <ng-template #linkedInitials>
+      <span class="font-semibold text-zinc-200" [class.text-xs]="size === 'sm'" [class.text-sm]="size === 'md'">{{ initial }}</span>
+    </ng-template>
+  </span>
+  <span *ngIf="showName" class="min-w-0 truncate font-medium text-zinc-200 hover:text-red-300">{{ resolvedName }}</span>
+  <span *ngIf="showName && resolvedVerified" class="shrink-0 text-xs text-emerald-300" title="Chaîne vérifiée">✓</span>
+</a>
+<ng-template #plainBlock>
+  <span class="flex min-w-0 flex-1 items-center gap-2">
+    <span class="flex shrink-0 items-center justify-center overflow-hidden rounded-full border border-zinc-700 bg-zinc-800"
+          [class.h-6]="size === 'sm'" [class.w-6]="size === 'sm'"
+          [class.h-8]="size === 'md'" [class.w-8]="size === 'md'">
+      <img *ngIf="resolvedAvatar; else plainInitials"
+           [src]="resolvedAvatar" [alt]="resolvedName" loading="lazy"
+           class="h-full w-full object-cover" referrerpolicy="no-referrer" />
+      <ng-template #plainInitials>
+        <span class="font-semibold text-zinc-200" [class.text-xs]="size === 'sm'" [class.text-sm]="size === 'md'">{{ initial }}</span>
+      </ng-template>
+    </span>
+    <span *ngIf="showName" class="min-w-0 truncate font-medium text-zinc-200">{{ resolvedName }}</span>
+    <span *ngIf="showName && resolvedVerified" class="shrink-0 text-xs text-emerald-300">✓</span>
+  </span>
+</ng-template>