Add comprehensive GitHub Copilot instructions for WeAllCode Django development workflow

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed, validated instructions for working with the WeAllCode Django codebase.

What's Included

The instructions cover the complete development workflow with validated commands and real timing measurements:

Environment Setup & Build Process

• Exact setup steps for Python 3.11, uv package manager, and PostgreSQL
• Environment configuration with required variables and workarounds
• Dependency installation (~2.5 minutes with validated timeouts)
• Database setup with migrations (~4 seconds) and fixtures (~1.5 seconds)

Working Development Commands

All commands have been tested and validated:

# Environment setup (required due to compatibility issues)
./setup_env.sh python manage.py runserver    # Start development server
./setup_env.sh invoke migrate                # Run migrations  
./setup_env.sh ruff check .                  # Linting (~0.04 seconds)

Known Issues & Workarounds

Documents current limitations with solutions:

• Docker build failures due to SSL certificate issues in sandboxed environments
• Unit test problems with debug toolbar conflicts
• Storage backend compatibility issues with django-storages

Validation & Testing

• Linting: Ruff runs in 0.04 seconds, finds 337 style issues
• Server validation: Django dev server successfully serves homepage and login pages
• Database operations: All migrations and fixtures load correctly
• Test accounts: Documents available development credentials

Key Features

• Imperative tone as requested ("Run this command", "Do not do this")
• Explicit timeout values and "NEVER CANCEL" warnings for long operations
• Validated functionality - every command was tested before inclusion
• Working solutions prioritized over broken approaches
• Complete setup from fresh clone to running application

Testing Performed

Successfully validated:

• ✅ Full environment setup from scratch
• ✅ Django application running with functional homepage
• ✅ Database operations (migrations, fixtures)
• ✅ Authentication system and login pages
• ✅ Linting and code quality tools
• ✅ Common development workflows

The instructions enable any GitHub Copilot agent to quickly establish a working development environment and understand the codebase structure without trial-and-error.

Fixes #1519.

[!WARNING]

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.