Refactor README: Simplify structure and move detailed docs to docs.md

[Copilot]

This PR completely refactors the README to address feedback about it being too long and difficult to read. The changes make the documentation more accessible while preserving all essential information.

Key Changes

README.md Simplification:

• Reduced from 345 to 145 lines (~58% reduction)
• Focused on essential quick-start information
• Preserved useful stack status tables and contribution guidelines
• Added clear folder structure documentation
• Fixed license badge inconsistency (MIT → Apache 2.0 to match LICENSE file)

New docs.md File:

• Created comprehensive documentation file with 208 lines
• Contains detailed installation, configuration, and troubleshooting guides
• Ready for integration into the Gitbook wiki as requested

Content Organization:

• README.md now covers: brief description, quick deployment, stack tables, contribution guidelines
• docs.md contains: detailed architecture, prerequisites, configuration, troubleshooting
• Removed redundant "useful links" section
• Maintained all stack progress tables (marked as very useful in feedback)

The folder structure information has been enhanced to clearly show the standard layout:

nom-du-stack/
├── compose.yaml    # Configuration Docker Compose
├── .env.template   # Template des variables d'environnement
├── .gitignore      # Fichiers à ignorer
└── config/         # Fichiers de configuration (optionnel)

This restructuring makes the README much more approachable for new users while ensuring all detailed documentation remains accessible in docs.md for the Gitbook integration.

Fixes #10.

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