decouple some config to .env + suggestion on security

[pietrobondioli]

Description:

This pull request introduces a .env.sample file for secure environment variable management and updates the Docker Compose files to use these variables. Additionally, the README is revised to guide users on setting up their .env file.

Key Changes:

• Added .env.sample with variables like HOME, PIHOLE_WEBPASSWORD, and KAIZOKU_DB_PASSWORD.
• Updated Docker Compose files to reference variables from .env.
• Updated README with instructions for using .env.sample.

Security Note:

• Rewrote history to remove hardcoded WEBPASSWORD. This change is on the main-safe-history
• Repository owner should consider force-pushing this branch to the main to remove the exposed credentials from history.

( I tried to open a pull request with the rewritten history but looks like github doesn't allow this kind of operation :/ )