A lock taken per tick passed between frontends on almost every tick, so
several frontends probed at once and each change of leader re-sent the
warm set and all state. The leader now holds a dedicated PostgreSQL
session with the advisory lock and keeps it until it shuts down or the
session dies.
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>