feat: métriques serveur dans footer dashboard + notification offline WS

server/db/db.go

@@ -234,13 +234,35 @@ func (d *DB) PruneOldMetrics(retentionDays int) error {
 }
 
 func (d *DB) MarkOffline(timeoutSec int64) error {
-	cutoff := time.Now().Unix() - timeoutSec
-	_, err := d.conn.Exec(
-		`UPDATE agents SET status='offline' WHERE last_seen < ? AND status != 'offline'`,
-		cutoff)
+	_, err := d.MarkOfflineAndGetIDs(timeoutSec)
 	return err
 }
 
+// MarkOfflineAndGetIDs marque les agents inactifs et retourne leurs IDs.
+func (d *DB) MarkOfflineAndGetIDs(timeoutSec int64) ([]string, error) {
+	cutoff := time.Now().Unix() - timeoutSec
+	rows, err := d.conn.Query(
+		`SELECT id FROM agents WHERE last_seen < ? AND status != 'offline'`, cutoff)
+	if err != nil {
+		return nil, err
+	}
+	var ids []string
+	for rows.Next() {
+		var id string
+		_ = rows.Scan(&id)
+		ids = append(ids, id)
+	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
+	rows.Close()
+	if len(ids) > 0 {
+		_, err = d.conn.Exec(
+			`UPDATE agents SET status='offline' WHERE last_seen < ? AND status != 'offline'`, cutoff)
+	}
+	return ids, err
+}
+
 func init() {
 	log.SetFlags(log.LstdFlags | log.Lshortfile)
 }