build(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [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/v4...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] <support@github.com>

.github/workflows/playwright.yml

@@ -9,7 +9,7 @@ jobs:
     timeout-minutes: 60
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: lts/*

package.json

@@ -111,7 +111,7 @@
     "@vitest/coverage-v8": "^3.2.4",
     "concurrently": "^9.2.0",
     "eslint": "^9.30.0",
-    "eslint-config-next": "^16.0.0",
+    "eslint-config-next": "^15.3.4",
     "eslint-plugin-prettier": "^5.5.1",
     "eslint-plugin-react-hooks": "^5.2.0",
     "jest-axe": "^10.0.0",