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/components/library/subscriptions/subscriptions.component.ts

@@ -1,7 +1,7 @@
 import { ChangeDetectionStrategy, Component, computed, inject, signal } from '@angular/core';
 import { CommonModule } from '@angular/common';
 import { DatePipe, DecimalPipe } from '@angular/common';
-import { Router } from '@angular/router';
+import { Router, RouterLink } from '@angular/router';
 import { SubscriptionsService, type SubscriptionItem } from '../../../services/subscriptions.service';
 import type { ProviderId } from '../../../app/shared/models/channel.model';
 import { ProviderBadgeComponent } from '../../../app/shared/components/provider-badge/provider-badge.component';
@@ -17,7 +17,7 @@ type SortKey = 'alpha' | 'recent' | 'subs';
 @Component({
   selector: 'app-library-subscriptions',
   standalone: true,
-  imports: [CommonModule, DatePipe, DecimalPipe, ProviderBadgeComponent, SubscribeButtonComponent],
+  imports: [CommonModule, DatePipe, DecimalPipe, RouterLink, ProviderBadgeComponent, SubscribeButtonComponent],
   templateUrl: './subscriptions.component.html',
   changeDetection: ChangeDetectionStrategy.OnPush,
 })