guides: add django

[craig-osterhout]

Description

Added simple Django guide.

https://deploy-preview-24851--docsdocker.netlify.app/guides/django/

Related issues or tickets

Closes #21277

Reviews

• Editorial review

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[craig-osterhout]

/review

[docker-agent]

Assessment: 🔴 CRITICAL

This PR adds a new Django guide to Docker docs. The guide is well-structured and covers a useful topic, but has several issues that need attention before merge:

• 1 HIGH finding: A Compose environment variable (DEBUG=1) is set but settings.py is never shown reading it from the environment, so it silently has no effect.
• 3 MEDIUM findings: Non-standard callout syntax, a broken ordered-list code block (missing indentation), and a factually incorrect YAML comment about Django's DEBUG setting and auto-reload.
• 1 MEDIUM finding: Marketing language ("simplify compliance") in the DHI section.

[craig-osterhout]

• Replaced docker init and Docker Official Images with Docker Hardened Images (DHI) throughout. The guide now uses DHI for both the Python app and PostgreSQL service.
• Switched from pip/requirements.txt to uv/pyproject.toml. All dependency management — bootstrapping, adding packages, and installing in the Dockerfile — now uses uv.
• Added two bootstrapping options. Users can scaffold the project with a local uv installation or entirely via a DHI dev container, with no local Python required.
• Updated PostgreSQL from postgres:17 (DOI) to dhi.io/postgres:18. Removed the user: postgres override since DHI postgres already runs as nonroot. Updated the volume mount path to /var/lib/postgresql to match DHI's data directory layout.
• Updated Alpine from 3.21 to 3.22.
• Updated Compose Watch triggers from requirements.txt to pyproject.toml and uv.lock.
• Added UV_LINK_MODE=copy to the Dockerfile builder stage and container bootstrap commands to suppress a hardlink warning that appears when the uv cache and build filesystem are on separate volumes.
• Fixed the project directory tree to reflect that uv now generates main.py instead of hello.py.
• Added a note on Windows shell syntax for the container bootstrap commands.

[craig-osterhout]

/review

[docker-agent]

Assessment: 🟡 NEEDS ATTENTION

Two medium-severity issues found in the new Django guide that could mislead users copying example code.