chore(deps): bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/docker-publish.yml

@@ -24,7 +24,7 @@ jobs:
       cancel-in-progress: false
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Set up QEMU (for multi-arch builds)
         uses: docker/setup-qemu-action@v4

.github/workflows/gh-page-publish.yml

@@ -21,7 +21,7 @@ jobs:
         working-directory: .
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Setup Flutter
         uses: subosito/flutter-action@v2

.github/workflows/pr-preview.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           repository: ${{ github.repository }}
           ref: refs/pull/${{ github.event.pull_request.number }}/merge

.github/workflows/pr-unit-tests.yml

@@ -23,7 +23,7 @@ jobs:
         working-directory: .
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         continue-on-error: true
         id: checkout_https
         with:
@@ -34,7 +34,7 @@ jobs:
 
       - name: Checkout repository via SSH (fallback)
         if: steps.checkout_https.outcome == 'failure'
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           repository: ${{ github.repository }}
           ref: refs/pull/${{ github.event.pull_request.number }}/merge