feat: Extract Wild Central as standalone Go service

Extract the Central networking functionality from wild-cloud/api into
a standalone service. Wild Central manages DNS (dnsmasq), gateway
(HAProxy), firewall (nftables), VPN (WireGuard), TLS (certbot),
security (CrowdSec), and DDNS — all the network appliance concerns.

All Cloud-specific code (instances, clusters, nodes, apps, backups,
operations, kubectl/talosctl tooling) has been removed. The API struct
and route registration contain only Central endpoints. Tests updated
to match the new API signature.

Builds and all tests pass.

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

internal/api/v1/helpers.go

@@ -0,0 +1,77 @@
+package v1
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/wild-cloud/wild-central/internal/sse"
+)
+
+// broadcastDnsmasqEvent broadcasts SSE events for dnsmasq status changes
+func (api *API) broadcastDnsmasqEvent(eventType string, message string) {
+	if api.sseManager == nil {
+		return
+	}
+
+	// Get current dnsmasq status
+	status, err := api.dnsmasq.GetStatus()
+	if err != nil {
+		status = nil
+	}
+
+	event := &sse.Event{
+		ID:           fmt.Sprintf("dnsmasq-%d", time.Now().UnixNano()),
+		Type:         eventType,
+		InstanceName: "global", // dnsmasq is global/central-level, not instance-specific
+		Timestamp:    time.Now(),
+		Data: map[string]any{
+			"message": message,
+			"status":  status,
+		},
+	}
+
+	api.sseManager.Broadcast(event)
+}
+
+// broadcastHaproxyEvent broadcasts SSE events for HAProxy status changes
+func (api *API) broadcastHaproxyEvent(eventType string, message string) {
+	if api.sseManager == nil {
+		return
+	}
+
+	event := &sse.Event{
+		ID:           fmt.Sprintf("haproxy-%d", time.Now().UnixNano()),
+		Type:         eventType,
+		InstanceName: "global",
+		Timestamp:    time.Now(),
+		Data: map[string]any{
+			"message": message,
+		},
+	}
+
+	api.sseManager.Broadcast(event)
+}
+
+// broadcastCentralStatusEvent broadcasts SSE events for central status changes
+func (api *API) broadcastCentralStatusEvent(startTime time.Time) {
+	if api.sseManager == nil {
+		return
+	}
+
+	uptime := time.Since(startTime)
+
+	event := &sse.Event{
+		ID:           fmt.Sprintf("central-%d", time.Now().UnixNano()),
+		Type:         "central:status",
+		InstanceName: "global",
+		Timestamp:    time.Now(),
+		Data: map[string]any{
+			"status":        "running",
+			"version":       api.version,
+			"uptime":        uptime.String(),
+			"uptimeSeconds": int(uptime.Seconds()),
+		},
+	}
+
+	api.sseManager.Broadcast(event)
+}