feat: Add Helm chart for keylocker deployment

[vpuhoff]

This commit introduces a Helm chart for deploying the keylocker Python application to Kubernetes. The chart is designed to facilitate debugging and running keylocker as a CLI tool or for Python applications using the keylocker library.

Key changes include:

1. Dockerfile: Added a Dockerfile to containerize the keylocker application and its dependencies.
2. Helm Chart (keylocker-chart/):
   • Generated a standard Helm chart structure.
   • Customized values.yaml to provide flexible configuration for the
     image, command/arguments, secret management (KEYLOCKER_SECRET_KEY,
     VAULT_ADDR, VAULT_TOKEN via Kubernetes Secrets), and mounting of
     custom configuration files or Python scripts via ConfigMaps.
   • Modified templates/deployment.yaml to dynamically configure the
     deployment based on values.yaml, including environment variables,
     secret sourcing, command overrides, and volume mounts.
   • Significantly rewrote templates/NOTES.txt to offer detailed
     guidance on chart installation, configuration, secret management,
     and usage examples for keylocker.
   • Removed unused templates like service.yaml, ingress.yaml, and
     hpa.yaml which are not relevant for a CLI tool by default.
   • Updated templates/tests/test-connection.yaml with a more
     appropriate test for a CLI application (verifies keylocker --help).
   • Ensured helm lint passes for the chart.
   • A basic README.md for the chart is intended (content prepared).

This chart allows you to run keylocker in your Kubernetes environment for processing YAML files with !SEC, !ENV, and !VAULT tags, or for running your own Python scripts that leverage the keylocker library for secret management.