feat: basic devcontainer and copilot instructions

[caviri]

Proposed Changes

This PR adds development container support to improve developer experience and onboarding. The changes include:

• DevContainer Configuration: Added VS Code development container setup with Python 3.12, uv package manager, and essential extensions pre-installed
• Environment Template: Provided .env.dist template file to guide configuration setup
• GitHub Copilot Instructions: Added comprehensive AI coding agent instructions to help with context-aware assistance during development

The development container automatically:

• Sets up the Python environment with the correct interpreter path
• Installs the project in editable mode using uv
• Forwards the FastAPI default port (7514) for easy testing
• Includes essential VS Code extensions (Python, Pylance, TOML support)

This addresses the need for consistent development environments and reduces setup friction for new contributors.

Types of Changes

What types of changes does your contribution introduce? Put an x in the boxes that apply

• A bug fix (non-breaking change which fixes an issue). Use MR tag bugfix.
• A new feature (non-breaking change which adds functionality). Use MR tag feature.
• A breaking change (fix or feature that would cause existing functionality to not work as expected). Use MR tag feature.
• A non-productive update (documentation, tooling, etc. if none of the other choices apply). Use MR tag chore.

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING guidelines.

Further Comments

The devcontainer setup leverages the existing uv-based build system and maintains consistency with the project's Python toolchain. The GitHub Copilot instructions provide detailed context about the RDF transformation architecture, development workflows, and project-specific conventions to enable more effective AI assistance.

This change is purely additive and doesn't affect the core functionality - it only improves the development experience for contributors working in VS Code with development containers enabled.