fix: plusieurs correctifs jobs et analyzer

- cancel_job: ajouter 'extracting_pages' aux statuts annulables
- cleanup_stale_jobs: couvrir 'extracting_pages' et 'generating_thumbnails' au redémarrage
- analyzer: ne pas régénérer le thumbnail si déjà existant (skip sub-phase B)
- analyzer: supprimer les dotfiles macOS (._*) encore en DB
- SSE backoffice: réduire le spam de logs en cas d'API injoignable

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

apps/api/src/index_jobs.rs

@@ -182,7 +182,7 @@ pub async fn cancel_job(
     id: axum::extract::Path<Uuid>,
 ) -> Result<Json<IndexJobResponse>, ApiError> {
     let rows_affected = sqlx::query(
-        "UPDATE index_jobs SET status = 'cancelled' WHERE id = $1 AND status IN ('pending', 'running', 'generating_thumbnails')",
+        "UPDATE index_jobs SET status = 'cancelled' WHERE id = $1 AND status IN ('pending', 'running', 'extracting_pages', 'generating_thumbnails')",
     )
     .bind(id.0)
     .execute(&state.pool)