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/templates/configmap.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ include "cv-app.fullname" . }}-config
+  labels:
+    {{- include "cv-app.labels" . | nindent 4 }}
+data:
+  PORT: "3001"
+  DB_PATH: "/app/data/cv.db"
+  AUTH_MODE: {{ .Values.backend.auth.mode | quote }}
+  {{- if eq .Values.backend.auth.mode "keycloak" }}
+  KEYCLOAK_URL: {{ .Values.backend.keycloak.url | quote }}
+  KEYCLOAK_REALM: {{ .Values.backend.keycloak.realm | quote }}
+  KEYCLOAK_CLIENT_ID: {{ .Values.backend.keycloak.clientId | quote }}
+  {{- end }}