ci: 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/auto-deploy.yml

@@ -18,7 +18,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Detect Service Type
         id: detect
@@ -48,7 +48,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Setup Node
         uses: actions/setup-node@v4
@@ -79,7 +79,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Install Railway CLI
         run: npm i -g @railway/cli

.github/workflows/security-scan.yml

@@ -25,7 +25,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v4
@@ -44,7 +44,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Run npm audit
         if: hashFiles('package.json') != ''

.github/workflows/self-healing.yml

@@ -15,7 +15,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Check Health
         id: health
@@ -65,7 +65,7 @@ jobs:
     
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       
       - name: Setup Node
         if: hashFiles('package.json') != ''