🔗 Environment variable injector for Docker run

When running containerized applications locally or across testing and production environments, developers often need to inject configuration settings stored in key-value .env files directly into Docker containers. Passing environment variables manually using multiple -e KEY=VALUE flags quickly becomes tedious, verbose, and error-prone.

While Docker natively supports the --env-file flag, it can be rigid—it lacks support for dynamically overriding dynamic host environment variables, programmatically inspecting injected keys before execution, or combining variable injection with standardized container runtime parameters (such as automatic port mapping, container naming, and dry-run output). This script bridges that gap by providing a CLI tool that parses .env files safely using python-dotenv, injects key-value pairs along with host-level environment fallbacks, validates prerequisites, and executes a clean docker run command via standard subprocessing.