feat: add MetalLB for on-premise LoadBalancer support

- Add MetalLB IPAddressPool (192.168.108.213/32) and L2Advertisement
  so the frontend gets a stable external IP on the LAN
- Change frontend service type: NodePort → LoadBalancer
- Add 'Setup MetalLB' stage in Jenkinsfile that installs MetalLB v0.14.8
  (idempotent) and applies the IP pool config before each deploy

After deploy: kubectl get svc frontend -n scrum-manager
should show EXTERNAL-IP: 192.168.108.213
App accessible at: http://192.168.108.213

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Jenkinsfile

@@ -110,6 +110,24 @@ pipeline {
             }
         }
 
+        stage('Setup MetalLB') {
+            steps {
+                withKubeConfig([credentialsId: "${K8S_CRED_ID}"]) {
+                    sh """
+                        # Install MetalLB if not already present (idempotent)
+                        kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.14.8/config/manifests/metallb-native.yaml
+
+                        # Wait for MetalLB controller and speaker to be ready
+                        kubectl rollout status deployment/controller -n metallb-system --timeout=90s
+                        kubectl rollout status daemonset/speaker    -n metallb-system --timeout=90s
+
+                        # Apply IP pool config — CRDs must be ready before this
+                        kubectl apply -f k8s/overlays/on-premise/metallb/
+                    """
+                }
+            }
+        }
+
         stage('Deploy to K8s') {
             steps {
                 withKubeConfig([credentialsId: "${K8S_CRED_ID}"]) {

k8s/base/frontend/service.yaml

@@ -6,7 +6,7 @@ metadata:
     app.kubernetes.io/name: frontend
     app.kubernetes.io/component: web
 spec:
-  type: NodePort
+  type: LoadBalancer
   ports:
     - port: 80
       targetPort: 80

k8s/overlays/on-premise/metallb/ipaddresspool.yaml

@@ -0,0 +1,8 @@
+apiVersion: metallb.io/v1beta1
+kind: IPAddressPool
+metadata:
+  name: scrum-manager-pool
+  namespace: metallb-system
+spec:
+  addresses:
+    - 192.168.108.213/32

k8s/overlays/on-premise/metallb/l2advertisement.yaml

@@ -0,0 +1,8 @@
+apiVersion: metallb.io/v1beta1
+kind: L2Advertisement
+metadata:
+  name: scrum-manager-l2
+  namespace: metallb-system
+spec:
+  ipAddressPools:
+    - scrum-manager-pool