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](actions/checkout@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>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     name: HTML Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Validate HTML
         run: |
           for f in $(find . -name "*.html" -not -path "./node_modules/*"); do
@@ -39,7 +39,7 @@ jobs:
     name: E2E Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: "20"
@@ -62,7 +62,7 @@ jobs:
     name: Lighthouse Audit
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v4
         with:
           node-version: "20"
@@ -89,7 +89,7 @@ jobs:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/configure-pages@v5
       - uses: actions/upload-pages-artifact@v3
         with:

.github/workflows/deploy.yml

@@ -18,7 +18,7 @@ jobs:
     name: Pre-Deploy Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Verify all required files exist and are non-empty
         run: |
@@ -85,7 +85,7 @@ jobs:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/configure-pages@v4
       - uses: actions/upload-pages-artifact@v3
         with:

.github/workflows/website-e2e.yml

@@ -11,7 +11,7 @@ jobs:
     name: Responsive Layout Tests (Playwright)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Node.js
         uses: actions/setup-node@v4
@@ -51,7 +51,7 @@ jobs:
     name: Visual Sanity (Screenshot Comparison)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Node.js
         uses: actions/setup-node@v4

.github/workflows/website-performance.yml

@@ -13,7 +13,7 @@ jobs:
     name: Lighthouse Desktop
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Node.js
         uses: actions/setup-node@v4
@@ -106,7 +106,7 @@ jobs:
     name: Lighthouse Mobile
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Node.js
         uses: actions/setup-node@v4

.github/workflows/website-sanity.yml

@@ -11,7 +11,7 @@ jobs:
     name: HTML Structure Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install html5validator
         run: pip install html5validator
@@ -166,7 +166,7 @@ jobs:
     name: Internal Link Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Check internal links
         run: |
@@ -229,7 +229,7 @@ jobs:
     name: CSS Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Check CSS syntax
         run: |
@@ -283,7 +283,7 @@ jobs:
     name: Mobile Compatibility Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Verify mobile-critical elements
         run: |
@@ -331,7 +331,7 @@ jobs:
     name: Cross-Page Consistency
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Check nav links and footer consistency
         run: |