Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -20,7 +20,7 @@ jobs:
         - python-version: '3.11'
           django-version: '<5.2'
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
       with:
         python-version: ${{ matrix.python-version }}
@@ -34,13 +34,13 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: make lint
 
   docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: make html

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions: write-all
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: uv build
     - run: uv mkdocs gh-deploy --force