Enhance chart and add support for external PostgreSQL and Redis

[FML128]

Major overhaul for the chart. Adds external PostgreSQL and Redis support and improve usability of the chart.

Key changes include:

Configuration and Flexibility Enhancements:

• Added support for external PostgreSQL and Redis instances, including validation to ensure required fields are set when using external services. [1] [2]
• Improved secrets management: every integration (Postgres, media servers, AI providers) now supports existingSecret, allowing credentials to be managed by external secret managers. [1] [2]

Helm Chart Logic and Template Updates:

• Added a new helper template audiomuse-ai.secretEnvVars to inject the correct secret references and keys into Flask and Worker containers, supporting both chart-generated and user-provided secrets.
• Updated the ConfigMap and deployment templates to correctly handle external service host/port and improved environment variable handling for all supported AI providers and media servers. [1] [2]

User Experience Improvements:

• Added a detailed NOTES.txt to guide users after deployment, including instructions for accessing the app via port-forwarding, LoadBalancer, or Ingress, and displaying the chosen media server, AI provider, and database/Redis configuration.

General Updates:

• Bumped chart version to 1.1.0 to reflect these significant improvements.

These changes make the chart more robust, easier to use in production environments, and much better documented for new users and operators.