docs: update documentation for prerequisites and contribution guidelines

[cristofima]

This PR updates documentation to reflect current prerequisites and adds comprehensive contribution guidelines. The changes include version requirement updates (Terraform 1.5→1.9, Node.js 18→20), two new documentation files (CONTRIBUTING.md and CHANGELOG.md), improved navigation with tables of contents, and expanded development commands.

Key Changes

• Updated minimum version requirements across all documentation (Terraform ≥1.9, Node.js 20+)
• Added CONTRIBUTING.md with guidelines for collaboration, local development setup, and commit conventions
• Added CHANGELOG.md documenting v1.0.0 release with comprehensive feature list

[Copilot]

Pull request overview

This PR updates documentation to reflect current prerequisites and adds comprehensive contribution guidelines. The changes include version requirement updates (Terraform 1.5→1.9, Node.js 18→20), two new documentation files (CONTRIBUTING.md and CHANGELOG.md), improved navigation with tables of contents, and expanded development commands.

Key Changes

• Updated minimum version requirements across all documentation (Terraform ≥1.9, Node.js 20+)
• Added CONTRIBUTING.md with guidelines for collaboration, local development setup, and commit conventions
• Added CHANGELOG.md documenting v1.0.0 release with comprehensive feature list

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
infrastructure/terraform/TERRAFORM_BEST_PRACTICES.md	Updated Terraform version reference from 1.5.0 to 1.9.8
infrastructure/terraform/README.md	Updated Terraform minimum version from ≥1.5 to ≥1.9
frontend/README.md	Updated Node.js requirement from 18+ to 20+
docs/README.md	Added Project Management section with links to CHANGELOG and CONTRIBUTING
docs/QUICKSTART.md	Updated Terraform prerequisite from ≥1.5 to ≥1.9
docs/PROJECT_REFERENCE.md	Added comprehensive table of contents for improved navigation
docs/LESSONS_LEARNED.md	Added table of contents with anchor links to all sections
README.md	Added version badges, updated prerequisites (Terraform ≥1.9, Node.js 20+), added links to CONTRIBUTING and CHANGELOG
CONTRIBUTING.md	New file with contribution guidelines, local setup, commit conventions, and project philosophy
CHANGELOG.md	New file documenting v1.0.0 release with all features, infrastructure, and documentation
.github/git-commit-messages-instructions.md	Added table of contents, expanded scope guidelines with full path examples, updated file type reference table
.github/copilot-instructions.md	Added architectural principle about autonomous training container, expanded development commands with Docker Compose examples, added testing & validation sections

[Copilot]

The line "- scripts/generate_architecture_diagram.py | Generate AWS architecture diagrams |" has inconsistent formatting. It starts with a dash - instead of a pipe | like the rows above it. This breaks the markdown table structure.

Should be:

| `scripts/generate_architecture_diagram.py` | Generate AWS architecture diagrams |

Suggested change

	- `scripts/generate_architecture_diagram.py` | Generate AWS architecture diagrams |
	| `scripts/generate_architecture_diagram.py` | Generate AWS architecture diagrams |