support env vars from .env files it in agent engine py deployment

The current deployment process relies exclusively on the --set-env-vars flag within our Makefile. This approach is cumbersome when managing multiple variables and makes it difficult to maintain separate configurations for different environments, leading to potential configuration errors and decreased developer productivity.

support for loading environment variables directly from .env files during deployment process.

Benefits
Eliminates the need to manually pass lengthy strings of variables in the terminal.
Environment Segregation: Simplifies the management of environment-specific configurations (e.g., dev, staging, prod) by using distinct .env files.
Maintainability: Centralizes configuration, making it easier to track and update variable sets.

Start with the deployment targets and existing --set-env-vars handling in the Makefile. Determine how deployment currently receives variables and define the .env loading behavior, including separate environment files; done means deployment can use those files without manually passing the full variable string.

Written by the indexing model from the issue text.