debug(sync): endpoint diag multi-endpoints (Data API + InnerTube) + bouton UI

src/components/library/import/import.component.html

@@ -101,7 +101,12 @@
         class="rounded-md border border-slate-700 bg-slate-800 px-3 py-1.5 text-sm text-slate-200 transition hover:border-slate-500">
         {{ ytChannelsLoading() ? 'Chargement…' : (ytChannels().length ? 'Recharger' : 'Lister mes chaînes') }}
       </button>
+      <button type="button" (click)="loadDiag()" [disabled]="diagLoading()"
+        class="rounded-md border border-slate-700 bg-slate-800 px-3 py-1.5 text-sm text-slate-200 transition hover:border-slate-500">
+        {{ diagLoading() ? 'Diagnostic…' : '🩺 Diagnostic complet' }}
+      </button>
     </div>
+    <pre *ngIf="diagResult()" class="mt-2 max-h-64 overflow-auto whitespace-pre-wrap rounded-lg border border-slate-700 bg-slate-950 p-2 text-xs text-slate-300">{{ diagResult() }}</pre>
     <div *ngIf="ytChannelsError()" class="mt-2 rounded-lg border border-red-700 bg-red-900/30 p-2 text-xs text-red-200">{{ ytChannelsError() }}</div>
     <div *ngIf="ytChannels().length" class="mt-3 space-y-2">
       <label *ngFor="let c of ytChannels()" class="flex cursor-pointer items-center gap-3 rounded-lg border border-slate-700 bg-slate-800/60 px-3 py-2 text-sm transition hover:border-slate-500">

src/components/library/import/import.component.ts

@@ -249,6 +249,24 @@ export class ImportComponent implements OnInit {
   ytSelectedChannelId = signal<string>('');
   ytSavingChannel = signal(false);
   ytChannelSaved = signal<string | null>(null);
+  diagLoading = signal(false);
+  diagResult = signal<string | null>(null);
+
+  loadDiag(): void {
+    if (this.diagLoading()) return;
+    this.diagLoading.set(true);
+    this.diagResult.set(null);
+    this.api.diag().subscribe({
+      next: (res) => {
+        this.diagResult.set(JSON.stringify(res, null, 1));
+        this.diagLoading.set(false);
+      },
+      error: (e) => {
+        this.diagResult.set(`Erreur diag : ${e?.error?.error || e?.message || 'diag_failed'}`);
+        this.diagLoading.set(false);
+      },
+    });
+  }
 
   loadYtChannels(): void {
     if (!this.isConnected('google') || this.ytChannelsLoading()) return;

src/services/oauth-import.service.ts

@@ -101,6 +101,11 @@ export class OAuthImportService {
   saveYtChannel(channelId: string | null, pageId: string | null): Observable<{ selected: { channelId: string | null; pageId: string | null } }> {
     return this.http.put<any>(`/api/oauth/google/yt-channel`, { channelId, pageId });
   }
+
+  /** Diagnostic : état de chaque endpoint authentifié (Data API + InnerTube). */
+  diag(): Observable<any> {
+    return this.http.get<any>(`/api/oauth/google/diag`);
+  }
 }
 
 /** Parse local du `watch-history.json` de Google Takeout (confidentiel : rien n'est uploadé tel quel). */