chore(deps): update actions/checkout action to v6

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/continuous-integration.yaml

@@ -22,7 +22,7 @@ jobs:
         ports:
           - 5432:5432
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v6
         with:
@@ -39,7 +39,7 @@ jobs:
     name: Code Lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 22 # LTS
@@ -52,7 +52,7 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.event.pull_request }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions/setup-node@v6