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/registry-secret.yaml.template

@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Secret
+metadata:
+  name: ${APP_NAME}-registry-secret
+  labels:
+    app: ${APP_NAME}
+    component: registry
+type: kubernetes.io/dockerconfigjson
+data:
+  .dockerconfigjson: ${REGISTRY_AUTH_BASE64}