Add git user configuration support

Add required git user configuration to enable commits from within the container.
This change ensures proper attribution of git commits made inside the container by:

- Adding GIT_USER_NAME and GIT_USER_EMAIL to .env.example
- Configuring git user globally during Docker build
- Adding documentation for git configuration requirements
- Updating README with clearer setup instructions and requirements

The configuration is now required as part of the initial setup to prevent
issues with unattributed commits when using git inside the container.

.env.example

@@ -1,6 +1,10 @@
 # Copy this file to .env and fill in your credentials
 # The .env file will be baked into the Docker image during build
 
+# Required: Git configuration for commits made inside the container
+GIT_USER_NAME=Your Name
+GIT_USER_EMAIL=your.email@example.com
+
 # Optional: Twilio credentials for SMS notifications
 TWILIO_ACCOUNT_SID=your_twilio_account_sid
 TWILIO_AUTH_TOKEN=your_twilio_auth_token