ci: bump checkout and setup-node actions to v5

GitHub forces action runtimes to Node 24 on 2026-06-16; the v4
actions pin Node 20 and warn in current runs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: zephyrie

.github/workflows/deploy.yml

@@ -16,10 +16,10 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
         with:
           persist-credentials: false
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v5
         with:
           node-version: 20
           cache: npm