Refactor: Move sensitive config to private file, improve ECS deployment & healthchecks

[nickykln]

Description

This pull request moves all sensitive configuration data (Firebase, Sentry, keys, etc.) into a private, non-versioned file environments.private.json, and updates the AWS Terraform infrastructure to dynamically load these secrets.
It also improves ECS deployment robustness (healthcheck management, etc.).

Changes

• Moved sensitive configuration to environments.private.json
• Loads environment variables via jsondecode(file(...)) in Terraform
• Added a .gitignore to protect sensitive files
• Increased ALB healthcheck timeouts to avoid interruptions during long migrations
• Fixed environment variables for CORS (MARBLE_APP_URL and MARBLE_BACKOFFICE_HOST now use the full URL)
• Updated the README to document the new organization

Additional Information

• Sensitive files in config/ are excluded from version control.

To test:

• Ensure Terraform deployment runs without errors
• Check that the application starts and endpoints are accessible

Screenshots

Not applicable for this configuration/infra PR.

Checklist

• Tests passed
• Manual QA done
• Documentation updated

[Pascal-Delange]

Hi @nickykln ,
Sorry I missed this PR 3 weeks ago. I'll check it out tomorrow.

[Pascal-Delange]

Hi @nickykln !
Thanks for the contribution.
Can I please send you our contributor license agreement before we merge this ? What email address can I send it to ?
Best,
Pascao

[nickykln]

Hi @Pascal-Delange
You can send it to nicolas@pixpay.fr.