fix: Kuma heartbeat status enum — 0 is DOWN, not 2

Live-path debug found the bridge silently ignored real Kuma down-events:
Kuma heartbeat.status is 0=down/1=up/2=pending, not the webhook-doc
guess used earlier. DOWN now keyed on 0.
Ticket: https://projects.knownelement.com/issues/824

cmd/bridge/main.go

@@ -199,7 +199,7 @@ func (b *bridge) handle(w http.ResponseWriter, r *http.Request) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 	switch status {
-	case 2: // DOWN (0=unknown,1=up,2=down per Kuma webhook)
+	case 0: // Kuma heartbeat status: 0=down, 1=up, 2=pending, 3=maintenance
 		if _, exists := b.open[k.Monitor.Name]; !exists {
 			tid, err := b.glpi.openTicketFor(k.Monitor.Name)
 			if err == nil && tid == 0 {