chore: remove legacy gitleaks.yml (ADR-011 GHAS migration)

.github/workflows/gitleaks.yml

@@ -1,30 +0,0 @@
-name: Secret Scanning (Gitleaks)
-
-on:
-  push:
-    branches: ['**']
-  pull_request:
-    branches: [main]
-  workflow_dispatch:
-
-permissions:
-  contents: read
-
-jobs:
-  scan:
-    name: Scan for secrets
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0  # Full history for accurate scanning
-
-      - name: Install Gitleaks
-        run: |
-          curl -sSfL https://github.com/gitleaks/gitleaks/releases/download/v8.30.0/gitleaks_8.30.0_linux_x64.tar.gz | tar -xz
-          sudo mv gitleaks /usr/local/bin/
-
-      - name: Run Gitleaks
-        run: gitleaks detect --source . --verbose