feat: scaffold agentmon services and k8s deploy

Adds Go microservices (ingest-gateway, event-processor, query-api, web-ui), NATS+Postgres wiring, initial schema/init job, ingress manifests for LAN+tailnet, and a multi-arch image build script.

internal/queue/nats/nats.go

@@ -0,0 +1,34 @@
+package nats
+
+import (
+	"context"
+	"time"
+
+	gnats "github.com/nats-io/nats.go"
+)
+
+type Publisher struct {
+	conn    *gnats.Conn
+	topic   string
+	timeout time.Duration
+}
+
+func NewPublisher(url, topic string) (*Publisher, error) {
+	conn, err := gnats.Connect(url)
+	if err != nil {
+		return nil, err
+	}
+	return &Publisher{conn: conn, topic: topic, timeout: 5 * time.Second}, nil
+}
+
+func (p *Publisher) Close() {
+	p.conn.Close()
+}
+
+func (p *Publisher) Publish(ctx context.Context, data []byte) error {
+	ctx, cancel := context.WithTimeout(ctx, p.timeout)
+	defer cancel()
+
+	_ = ctx
+	return p.conn.Publish(p.topic, data)
+}