feat: add Kubernetes Kustomize deployment manifests

Add k8s/base/ directory with Kustomize manifests for deploying
the scrum-manager application to Kubernetes:

- Namespace (scrum-manager)
- MySQL: Deployment, Service, PVC, Secret
- Backend: Deployment (2 replicas) with init container, Service
- Frontend: Deployment (2 replicas), Service (NodePort), ConfigMap (nginx.conf)

All deployments include resource requests/limits, liveness/readiness
probes, and proper label selectors.

k8s/base/frontend/deployment.yaml

@@ -0,0 +1,58 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: frontend
+  labels:
+    app.kubernetes.io/name: frontend
+    app.kubernetes.io/component: web
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: frontend
+      app.kubernetes.io/component: web
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: frontend
+        app.kubernetes.io/component: web
+    spec:
+      containers:
+        - name: frontend
+          image: scrum-frontend:latest
+          imagePullPolicy: IfNotPresent
+          ports:
+            - containerPort: 80
+              name: http
+          volumeMounts:
+            - name: nginx-config
+              mountPath: /etc/nginx/conf.d/default.conf
+              subPath: default.conf
+              readOnly: true
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 200m
+              memory: 128Mi
+          livenessProbe:
+            httpGet:
+              path: /
+              port: http
+            initialDelaySeconds: 10
+            periodSeconds: 10
+            timeoutSeconds: 3
+            failureThreshold: 3
+          readinessProbe:
+            httpGet:
+              path: /
+              port: http
+            initialDelaySeconds: 5
+            periodSeconds: 5
+            timeoutSeconds: 3
+            failureThreshold: 3
+      volumes:
+        - name: nginx-config
+          configMap:
+            name: frontend-nginx-config