Add support to manually set the ROOT_DIR

[chlima88]

Description:

It would be really helpful if we could manually set the ROOT_DIR .

Propose:

We can use the .env file to define a custom directory, together with a helper class that builds the paths, checks whether the variable is set, and applies the current path as a default value.

Benefits:

• Configuration flexibility – allows setting a custom ROOT_DIR without changing the source code.
• Portability – makes it easier to run the project across different environments (development, staging, production) just by changing environment variables.
• Future scalability – the structure is ready for other environment-driven configs if needed.
• Improved contributor experience – new developers can get started quickly by just adjusting the .env file.

[threat-punter]

I'm looking at moving Content Manager to its own GitHub repo before working on new features and enhancements. I'll leave this issue open in the meantime. Thanks again for opening this.