feat: Add container registry support and Kustomize foundation

- Add registry secret template for private container registry authentication
- Fix frontend deployment to use imagePullSecrets for private registry
- Enhance deploy-k8s.sh with registry authentication handling
- Add PVC storage size validation to prevent storage reduction errors
- Add graceful StatefulSet update error handling
- Fix template variable substitution for DOCKER_IMAGE
- Remove conflicting static PVC file that had unprocessed template variables
- Add Kustomize structure as alternative to shell script templates:
  - Base configuration with common resources
  - Development overlay with dev-specific configurations
  - Support for environment-specific image tags and resource limits

Registry setup requires setting REGISTRY_USERNAME, REGISTRY_PASSWORD, and
optionally REGISTRY_HOST in .env file for private registry authentication.

k8s-kustomize/base/frontend-deployment.yaml

@@ -0,0 +1,45 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: rxminder-frontend
+  labels:
+    component: frontend
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      component: frontend
+  template:
+    metadata:
+      labels:
+        component: frontend
+    spec:
+      imagePullSecrets:
+        - name: rxminder-registry-secret
+      containers:
+        - name: frontend
+          image: frontend-image
+          ports:
+            - containerPort: 80
+          envFrom:
+            - configMapRef:
+                name: rxminder-config
+          resources:
+            requests:
+              memory: '32Mi'
+              cpu: '20m'
+            limits:
+              memory: '64Mi'
+              cpu: '40m'
+          livenessProbe:
+            httpGet:
+              path: /
+              port: 80
+            initialDelaySeconds: 30
+            periodSeconds: 30
+          readinessProbe:
+            httpGet:
+              path: /
+              port: 80
+            initialDelaySeconds: 5
+            periodSeconds: 5

k8s-kustomize/base/kustomization.yaml

@@ -0,0 +1,60 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+metadata:
+  name: rxminder-base
+
+namespace: rxminder
+
+resources:
+  - frontend-deployment.yaml
+  - frontend-service.yaml
+  - couchdb-statefulset.yaml
+  - couchdb-service.yaml
+  - couchdb-pvc.yaml
+  - ingress.yaml
+  - configmap.yaml
+  - network-policy.yaml
+  - hpa.yaml
+  - db-seed-job.yaml
+
+# Common labels applied to all resources
+commonLabels:
+  app: rxminder
+  version: v1.0.0
+
+# Generate ConfigMap from environment files
+configMapGenerator:
+  - name: rxminder-config
+    envs:
+      - config.env
+
+# Generate Secret for CouchDB
+secretGenerator:
+  - name: couchdb-secret
+    literals:
+      - username=admin
+      - password=changeme
+    type: Opaque
+
+  # Generate registry secret from credentials
+  - name: rxminder-registry-secret
+    files:
+      - .dockerconfigjson=registry-config.json
+    type: kubernetes.io/dockerconfigjson
+
+# Images to be used (can be overridden in overlays)
+images:
+  - name: frontend-image
+    newName: gitea-http.taildb3494.ts.net/will/rxminder
+    newTag: latest
+  - name: couchdb-image
+    newName: couchdb
+    newTag: 3.3.2
+
+# Replicas (can be overridden in overlays)
+replicas:
+  - name: rxminder-frontend
+    count: 1
+  - name: rxminder-couchdb
+    count: 1