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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📥 Checkout Code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: ☕ Setup Java ${{ env.JAVA_VERSION }}
         uses: actions/setup-java@v4
@@ -40,7 +40,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "📥 Checkout Code (Full History)"
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0