feat: Add Helm chart for Kubernetes deployment (#1)

## Description

Add complete Helm chart for deploying the CV application to Kubernetes. The chart includes all necessary resources for a production-ready deployment with persistent storage and configurable authentication modes.

## Type of Change

- [x] `feat` - New feature (minor version bump)

## Breaking Changes

- [ ] This is a breaking change (major version bump)

**If breaking, describe the migration path:**

## Checklist

- [x] Commit messages follow [Conventional Commits](CONTRIBUTING.md#commit-guidelines)
- [x] Lint passes (`npm run lint`) - N/A for Helm charts
- [x] Build succeeds (`npm run build`) - N/A for Helm charts
- [x] Tests pass (`npm run test:run`) - N/A for Helm charts
- [ ] API documentation updated (if applicable)

## Testing

- `helm lint` passes on the chart
- `helm template test-release helm/cv-app/` renders 214 lines of valid Kubernetes manifests
- Verified all template helpers function correctly
- Tested conditional rendering (persistence enabled/disabled, simple/keycloak auth modes)

## Screenshots (if applicable)

N/A

## Related Issues

Implements the Helm chart design from `docs/plans/2026-02-23-helm-chart-design.md`

Co-authored-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>
Reviewed-on: #1

helm/cv-app/values.yaml

@@ -0,0 +1,57 @@
+frontend:
+  replicaCount: 1
+  image:
+    repository: username/cv-app
+    tag: latest
+    pullPolicy: IfNotPresent
+  resources: {}
+
+backend:
+  replicaCount: 1
+  image:
+    repository: username/cv-app-backend
+    tag: latest
+    pullPolicy: IfNotPresent
+  auth:
+    mode: simple
+    jwtSecret: ""
+  keycloak:
+    url: ""
+    realm: ""
+    clientId: ""
+  resources: {}
+
+persistence:
+  enabled: true
+  size: 1Gi
+  storageClass: ""
+
+ingress:
+  enabled: true
+  className: ""
+  annotations: {}
+  hosts:
+    - host: cv.local
+      paths:
+        - path: /api
+          service: backend
+        - path: /
+          service: frontend
+  tls: []
+
+imagePullSecrets: []
+nameOverride: ""
+fullnameOverride: ""
+
+serviceAccount:
+  create: true
+  annotations: {}
+  name: ""
+
+podAnnotations: {}
+podSecurityContext: {}
+securityContext: {}
+
+nodeSelector: {}
+tolerations: []
+affinity: {}