fix: Use configured dnsmasq IP instead of auto-detect

The auto-detect picks the default route interface (wlan0 at
192.168.8.152) but dnsmasq is bound to eth0 (192.168.8.151).
Now uses cloud.dnsmasq.ip from config as the Central IP for DNS
entries, falling back to auto-detect only if not configured.

Fixes DNS resolution failures when dnsmasq config points services
to the wrong interface IP.

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

internal/api/v1/helpers.go

@@ -104,7 +104,12 @@ func (api *API) reconcileNetworking() {
 	// DNS target IP depends on service type:
 	//   tcp-passthrough (k8s): DNS → k8s LB IP (LAN traffic goes direct to k8s)
 	//   http/static: DNS → Central IP (HAProxy terminates TLS)
-	centralIP, _ := network.GetWildCentralIP()
+	// Use the configured dnsmasq IP (eth0) as Central's IP, not auto-detected
+	// (auto-detect can pick wlan0 if that's the default route).
+	centralIP := globalCfg.Cloud.Dnsmasq.IP
+	if centralIP == "" {
+		centralIP, _ = network.GetWildCentralIP()
+	}
 	if centralIP == "" {
 		centralIP = "127.0.0.1"
 	}

internal/dnsmasq/config.go

@@ -36,13 +36,21 @@ func (g *ConfigGenerator) GetConfigPath() string {
 // Generate creates a dnsmasq configuration from the app config
 // It auto-detects the Wild Central server's IP address
 func (g *ConfigGenerator) Generate(cfg *config.GlobalConfig, clouds []config.InstanceConfig) string {
-	// Get the Wild Central IP address
-	dnsIP, err := network.GetWildCentralIP()
+	// Use configured dnsmasq IP (bound to eth0), falling back to auto-detect.
+	// Auto-detect can pick wlan0 if that's the default route, which is wrong
+	// when dnsmasq is only listening on eth0.
+	dnsIP := ""
+	if cfg != nil {
+		dnsIP = cfg.Cloud.Dnsmasq.IP
+	}
+	if dnsIP == "" {
+		var err error
+		dnsIP, err = network.GetWildCentralIP()
 		if err != nil {
 			slog.Error("failed to detect Wild Central IP", "component", "dnsmasq", "op", "generate", "error", err)
-		// Fall back to empty string if detection fails
 			dnsIP = ""
 		}
+	}
 
 	resolution_section := ""
 	for _, cloud := range clouds {