chore(dev): add prek git hooks for Python, ruff, uv and Django

[matrixise]

Summary

Set up prek, a Rust drop-in replacement for pre-commit that reads .pre-commit-config.yaml, with a base set of hooks for Python, ruff, uv and Django.

Installation choice

Like uv, prek is a machine tool, not a project dependency: it is not in pyproject.toml nor uv.lock. It is pinned in mise.toml next to uv (mise install), and can also be installed with brew install prek or uv tool install prek. Then run prek install in the clone. The ruff and Django hooks still need the project environment (uv sync --all-groups).

Hooks

• pre-commit-hooks v6.0.0: trailing-whitespace, end-of-file-fixer, mixed-line-ending (LF), check-yaml, check-toml, check-json, check-merge-conflict, check-case-conflict, check-added-large-files (500 KB), debug-statements, detect-private-key
• astral-sh/uv-pre-commit 0.12.19: uv-lock (rev aligned with the uv pinned in mise.toml and the dev group)
• django-upgrade 1.32.0: --target-version 6.0
• local hooks through uv run --frozen: ruff check --fix, ruff format, manage.py check, manage.py makemigrations --check --dry-run

Ruff runs as a local hook instead of astral-sh/ruff-pre-commit: the version comes from uv.lock, so the hook, CI and the editor cannot drift, and there is no rev to keep aligned with pyproject.toml.

The Django hooks unset DATABASE_URL so they always use the local SQLite database, even when a shell exports a remote DATABASE_URL.

Vendored assets under pythonie/core/static/{css,fonts,js} (Bootstrap, Font Awesome, SmartMenus) are excluded.

Not added: djLint. On the current templates it reports 12 lint errors (missing lang/alt, type on scripts, orphan tag, tag spacing) and would reformat all 13 templates. It is worth a follow-up PR that fixes the templates first.

Fixes from the first prek run --all-files (separate commits)

• style: whitespace/EOF only: .coveragerc, CLAUDE.md, development.env, base.html, core/meetup.html, core/segment.html, navbar_tree.html
• refactor: django-upgrade: drop USE_L10N (removed in Django 5.0), include from django.urls, path() instead of re_path() for the admin/ and documents/ prefixes, @admin.register in sponsors/admin.py

No behavior change.

CI

New prek job in test.yml, parallel to the existing test job: uv sync --all-groups (for the local ruff and Django hooks), then j178/prek-action@v3.0.0, which installs prek, caches the hook environments and runs prek run --show-diff-on-failure --all-files. The existing ruff, pip-audit and test steps are kept unchanged: the ruff steps overlap with the hooks but take under a second and remain the explicit gates of the test job.

Renovate

The pre-commit manager is disabled by default in Renovate: it is now enabled. Hook revisions are grouped in a weekly "pre-commit hooks" PR, and astral-sh/uv-pre-commit joins the existing uv group so it moves together with the uv dev dependency, Dockerfile and mise.toml.

Docs

README.md, CONTRIBUTING.md, DEVELOPMENT.md and CLAUDE.md: uv and prek listed as prerequisites, a uv sync --all-groups && prek install step in both the Docker and the local setup guides (the hooks run on the host even with Docker), usage, and emergency bypass (SKIP=<hook-id>, git commit --no-verify).

Test plan

• prek run --all-files: all hooks pass
• uv run ruff format --check pythonie and uv run ruff check pythonie
• uv run python pythonie/manage.py test pythonie --settings=pythonie.settings.tests (SQLite): 7 tests OK
• renovate-config-validator renovate.json
• CI green (prek job and test job)

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