Splitting .env Into YAML (High Priority)

[MrJs133]

Currently, we store all user configurations (such as graph server and LLM settings) in the .env file.

We need to refactor the .env file by splitting it and managing most user configurations with YAML.

Better to keep them in one yaml file first

Advanced:
Use a better/graceful way to manage Config(Like in C++/Java/Go we could read the updated config automatically by a config lib/frame -- auto refresh the memory & reload the config) --- like Omegaconf

Also the Config object should be more user friendly to modify:)