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] <[email protected]>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -30,7 +30,7 @@ jobs:
     runs-on: ${{ matrix.os.name }}
     steps:
       - name: ⬆️ Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install yq
         if: ${{ matrix.os.name == 'windows-2025' }}
         run: choco install yq
@@ -67,7 +67,7 @@ jobs:
     if: github.event_name != 'pull_request'
     steps:
       - name: ⬆️ Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set Docker tag
         id: docker_tag
         run: |
@@ -109,7 +109,7 @@ jobs:
       - build-server
     steps:
       - name: ⬆️ Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         env:
           CI_PAT: ${{ secrets.CI_PAT }}
         with:

.github/workflows/dart.yml

@@ -14,9 +14,9 @@ jobs:
         working-directory: ${{ matrix.projects }}
     steps:
       - name: ⬆️ Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - uses: dart-lang/setup-dart@v1
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Print Dart SDK version
         run: |
           dart --version

.github/workflows/deploy.yml

@@ -14,7 +14,7 @@ jobs:
       run:
         working-directory: docs
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install pnpm
         uses: pnpm/action-setup@v4
         with:
@@ -49,7 +49,7 @@ jobs:
         working-directory: server
     steps:
       - name: ⬆️ Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Extract Dart SDK version from pubspec.yaml
         id: dart_version
         shell: bash

.github/workflows/post_release.yml

@@ -18,7 +18,7 @@ jobs:
       IS_PRERELEASE: ${{ github.event.release.prerelease }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
           token: ${{ secrets.GITHUB_TOKEN }}