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/backend/deployment.yaml

@@ -0,0 +1,84 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: backend
+  labels:
+    app.kubernetes.io/name: backend
+    app.kubernetes.io/component: api
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: backend
+      app.kubernetes.io/component: api
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: backend
+        app.kubernetes.io/component: api
+    spec:
+      initContainers:
+        - name: wait-for-mysql
+          image: busybox:1.36
+          command:
+            - sh
+            - -c
+            - |
+              echo "Waiting for MySQL to be ready..."
+              until nc -z mysql 3306; do
+                echo "MySQL is not ready yet, retrying in 3s..."
+                sleep 3
+              done
+              echo "MySQL is ready!"
+      containers:
+        - name: backend
+          image: scrum-backend:latest
+          imagePullPolicy: IfNotPresent
+          ports:
+            - containerPort: 3001
+              name: http
+          env:
+            - name: DB_HOST
+              value: mysql
+            - name: DB_PORT
+              value: "3306"
+            - name: DB_USER
+              valueFrom:
+                secretKeyRef:
+                  name: mysql-secret
+                  key: DB_USER
+            - name: DB_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: mysql-secret
+                  key: DB_PASSWORD
+            - name: DB_NAME
+              valueFrom:
+                secretKeyRef:
+                  name: mysql-secret
+                  key: DB_NAME
+            - name: PORT
+              value: "3001"
+          resources:
+            requests:
+              cpu: 100m
+              memory: 128Mi
+            limits:
+              cpu: 500m
+              memory: 256Mi
+          livenessProbe:
+            httpGet:
+              path: /api/health
+              port: http
+            initialDelaySeconds: 15
+            periodSeconds: 10
+            timeoutSeconds: 3
+            failureThreshold: 3
+          readinessProbe:
+            httpGet:
+              path: /api/health
+              port: http
+            initialDelaySeconds: 5
+            periodSeconds: 5
+            timeoutSeconds: 3
+            failureThreshold: 5

k8s/base/backend/service.yaml

@@ -0,0 +1,17 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: backend
+  labels:
+    app.kubernetes.io/name: backend
+    app.kubernetes.io/component: api
+spec:
+  type: ClusterIP
+  ports:
+    - port: 3001
+      targetPort: 3001
+      protocol: TCP
+      name: http
+  selector:
+    app.kubernetes.io/name: backend
+    app.kubernetes.io/component: api