chore: pin dependencies to SHA digests for OpenSSF scorecard (#104)

Pin scorecard-action and codeql-action to commit SHA in scorecard.yml.
Pin base images to digest in Dockerfile.redos and Dockerfile.astra.
Replace curl|bash with direct binary download for actionlint.
Remove unused pip install cargo-audit-sarif.

.github/workflows/ci.yml

@@ -37,7 +37,10 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
       - name: Install actionlint
-        run: bash <(curl -s https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
+        run: |
+          ACTIONLINT_VERSION=1.7.12
+          curl -sLO "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz"
+          tar xzf "actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz" actionlint
       - name: Run actionlint
         run: ./actionlint -ignore "shellcheck reported issue" -ignore "SC[0-9]"
 
@@ -116,7 +119,6 @@ jobs:
       - name: Upload cargo-audit results as SARIF
         if: always()
         run: |
-          pip install --quiet cargo-audit-sarif 2>/dev/null || true
           python3 -c "
           import json, sys
           sarif = {

.github/workflows/scorecard.yml

@@ -24,7 +24,7 @@ jobs:
           persist-credentials: false
 
       - name: Run OpenSSF Scorecard
-        uses: ossf/scorecard-action@v2.4.3
+        uses: ossf/scorecard-action@4eaacf0543bb3f2c246792bd56e8cdeffafb205a # v2.4.3
         with:
           results_file: results.sarif
           results_format: sarif
@@ -32,7 +32,7 @@ jobs:
           repo_token: ${{ secrets.SCORECARD_TOKEN || secrets.GITHUB_TOKEN }}
 
       - name: Upload Scorecard results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@v4 # tag required by scorecard webapp verification
+        uses: github/codeql-action/upload-sarif@a60c4df7a135c7317c1e9ddf9b5a9b07a910dda9 # v4
         with:
           sarif_file: results.sarif
           category: scorecard