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/frontend-deployment.yaml.template

@@ -17,9 +17,11 @@ spec:
         app: ${APP_NAME}
         component: frontend
     spec:
+      imagePullSecrets:
+        - name: ${APP_NAME}-registry-secret
       containers:
         - name: frontend
-          image: ${DOCKER_IMAGE:-gitea-http.taildb3494.ts.net/will/${APP_NAME}:latest}
+          image: ${DOCKER_IMAGE}
           ports:
             - containerPort: 80
           envFrom: