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/configmap.yaml

@@ -0,0 +1,31 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: frontend-nginx-config
+  labels:
+    app.kubernetes.io/name: frontend
+    app.kubernetes.io/component: web
+data:
+  default.conf: |
+    server {
+        listen 80;
+        server_name localhost;
+
+        root /usr/share/nginx/html;
+        index index.html;
+
+        # Serve static files
+        location / {
+            try_files $uri $uri/ /index.html;
+        }
+
+        # Proxy API requests to backend service
+        location /api/ {
+            proxy_pass http://backend:3001;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection 'upgrade';
+            proxy_set_header Host $host;
+            proxy_cache_bypass $http_upgrade;
+        }
+    }