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

Author: renovate[bot]

.github/workflows/cli.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out frontend
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - uses: actions/setup-node@v5
         with:
           node-version: 24

.github/workflows/e2e.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out backend
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: brocoders/nestjs-boilerplate
           # Use token for private repository
@@ -26,7 +26,7 @@ jobs:
       - run: cd backend && ./wait-for-it.sh localhost:3001 -- echo "Backend is up"
 
       - name: Check out frontend
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - uses: actions/setup-node@v5
         with:
           node-version: 24