Update all GitHub Actions to latest major versions

checkout v4→v6, setup-node v4→v6, cache v4→v5,
upload-artifact v4→v7, download-artifact v4→v8,
upload-pages-artifact v3→v4, deploy-pages v4→v5

Resolves Node.js 20 deprecation warnings.

Author: planetf1

.github/workflows/nextjs.yml

@@ -20,8 +20,8 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
         with:
           node-version: "22"
           cache: "npm"
@@ -38,7 +38,7 @@ jobs:
       !contains(github.event.head_commit.message, '[skip link check]') &&
       vars.SKIP_LINK_CHECK != 'true'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: lycheeverse/lychee-action@v2
         with:
           # Check all markdown source files for broken links.
@@ -56,8 +56,8 @@ jobs:
   test-unit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
         with:
           node-version: "22"
           cache: "npm"
@@ -68,44 +68,44 @@ jobs:
     needs: [lint]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
         with:
           node-version: "22"
           cache: "npm"
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: .next/cache
           key: ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json') }}-${{ hashFiles('**.[jt]s', '**.[jt]sx') }}
           restore-keys: |
             ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json') }}-
       - run: npm ci
       - run: npm run build
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         with:
           name: website
           path: ./out
-      - uses: actions/upload-pages-artifact@v3
+      - uses: actions/upload-pages-artifact@v4
         with:
           path: ./out
 
   test-e2e:
     needs: [build]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
         with:
           node-version: "22"
           cache: "npm"
       - run: npm ci
       - run: npx playwright install --with-deps chromium
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: website
           path: ./out
       - run: npm run test:e2e
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         if: failure()
         with:
           name: playwright-report
@@ -123,5 +123,5 @@ jobs:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
-      - uses: actions/deploy-pages@v4
+      - uses: actions/deploy-pages@v5
         id: deployment