fix: detect publish_video permission error + show required permissions in Pages UI

- Detect Facebook error subcode 1363042 (missing publish_video permission)
  and throw a clear actionable message explaining how to fix it
- Add permission notice banner in Pages admin showing the 3 required
  Facebook permissions: pages_manage_posts, pages_read_engagement, publish_video

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/pages/pages.tsx

@@ -126,6 +126,22 @@ export default function PagesManagement() {
             <EditPageDialog page={editingPage} onOpenChange={(open) => !open && setEditingPage(null)} />
           </div>
 
+          {/* Permissions required notice */}
+          <div className="mb-6 p-4 bg-amber-500/10 border border-amber-500/30 rounded-xl flex gap-3">
+            <AlertTriangle className="w-5 h-5 text-amber-500 shrink-0 mt-0.5" />
+            <div className="text-sm">
+              <p className="font-semibold text-amber-600 dark:text-amber-400 mb-1">Permissions Facebook requises pour la publication vidéo</p>
+              <p className="text-muted-foreground mb-2">
+                Le token de page doit inclure : <code className="bg-muted px-1 rounded text-xs">pages_manage_posts</code>{" "}
+                <code className="bg-muted px-1 rounded text-xs">pages_read_engagement</code>{" "}
+                <code className="bg-muted px-1 rounded text-xs">publish_video</code>
+              </p>
+              <p className="text-muted-foreground text-xs">
+                Dans Graph API Explorer → Sélectionnez votre app → Ajoutez ces 3 permissions → Générez un User Token → Échangez via <code className="bg-muted px-1 rounded">/me/accounts</code> pour obtenir le Page Token.
+              </p>
+            </div>
+          </div>
+
           <div className="flex gap-3 mb-6">
             <Button
               variant="outline"

server/services/facebook.ts

@@ -592,7 +592,16 @@ export class FacebookService {
     console.log('📤 Facebook START response:', startRaw);
     const startData = JSON.parse(startRaw) as any;
     if (!startRes.ok || startData.error) {
-      throw new Error(`Facebook upload START error: ${startData.error?.message ?? startRaw} (code: ${startData.error?.code}, subcode: ${startData.error?.error_subcode})`);
+      const subcode = startData.error?.error_subcode;
+      if (subcode === 1363042) {
+        throw new Error(
+          `Le token Facebook de la page "${page.pageName}" n'a pas la permission "publish_video". ` +
+          `Régénérez le token dans Graph API Explorer en ajoutant les permissions : ` +
+          `pages_manage_posts, pages_read_engagement, publish_video. ` +
+          `(code: ${startData.error?.code}, subcode: ${subcode})`
+        );
+      }
+      throw new Error(`Facebook upload START error: ${startData.error?.message ?? startRaw} (code: ${startData.error?.code}, subcode: ${subcode})`);
     }
     const { upload_session_id, video_id } = startData;
     let startOffset: number = parseInt(startData.start_offset ?? '0', 10);