Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/ci.yml

@@ -14,7 +14,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'
@@ -34,7 +34,7 @@ jobs:
       matrix:
         python-version: ['3.12', '3.13']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
@@ -50,7 +50,7 @@ jobs:
   test-frontend:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: '22'
@@ -70,7 +70,7 @@ jobs:
   security:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'
@@ -86,7 +86,7 @@ jobs:
     needs: [test, test-frontend]
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
       - name: Build API image

.github/workflows/docs.yml

@@ -9,7 +9,7 @@ jobs:
   deploy-docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
       contents: write
       packages: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'