feat: Self-register Wild Central on startup

On startup, Wild Central registers its own domain (from config
cloud.central.domain) as an HTTP service with itself. This creates
the DNS entry, proxy route, and TLS cert needed to access the
Central UI via its domain name.

Registration is idempotent — safe on every restart. Skips silently
if no domain is configured. Logs a warning if registration fails.

Verified: after startup, /api/v1/services shows wild-central
registered with domain central.payne.io.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/api/v1/handlers.go

@@ -97,6 +97,40 @@ func envOrDefault(key, defaultVal string) string {
 	return defaultVal
 }
 
+// RegisterSelf registers Wild Central's own UI as a service so it gets
+// DNS + proxy + TLS via its own networking stack. Idempotent — safe to
+// call on every startup. Skips silently if no domain is configured.
+func (api *API) RegisterSelf(port int) {
+	globalConfigPath := filepath.Join(api.dataDir, "config.yaml")
+	globalCfg, err := config.LoadGlobalConfig(globalConfigPath)
+	if err != nil {
+		return
+	}
+
+	domain := globalCfg.Cloud.Central.Domain
+	if domain == "" {
+		return
+	}
+
+	svc := services.Service{
+		Name:   "wild-central",
+		Source: "wild-central",
+		Domain: domain,
+		Backend: services.Backend{
+			Address: fmt.Sprintf("127.0.0.1:%d", port),
+			Type:    services.BackendHTTP,
+		},
+		Reach: services.ReachInternal,
+		TLS:   services.TLSTerminate,
+	}
+
+	if err := api.services.Register(svc); err != nil {
+		slog.Warn("failed to self-register", "domain", domain, "error", err)
+	} else {
+		slog.Info("registered wild-central", "domain", domain)
+	}
+}
+
 // StartDDNS loads DDNS config and starts the background goroutine.
 func (api *API) StartDDNS(ctx gocontext.Context) {
 	api.ctx = ctx