fix: update gitleaks installation comments and add Node.js setup step

Author: h4rkl

.github/workflows/security.yml

@@ -25,6 +25,9 @@ jobs:
       - name: Install gitleaks
         env:
           GITLEAKS_VERSION: "8.30.1"
+          # Pinned binary. Verify against the official checksums when bumping:
+          # https://github.com/gitleaks/gitleaks/releases/download/v8.30.1/gitleaks_8.30.1_checksums.txt
+          # (line: gitleaks_8.30.1_linux_x64.tar.gz)
           GITLEAKS_SHA256: "551f6fc83ea457d62a0d98237cbad105af8d557003051f41f3e7ca7b3f2470eb"
         run: |
           set -euo pipefail
@@ -46,6 +49,10 @@ jobs:
         with:
           version: 10.15.1
           run_install: false
+      - name: Install Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: .node-version
       - name: Audit production dependencies
         # Fails on High/Critical advisories per the Solana Foundation SDLC.
         # Known-unfixable advisories are ignored via auditConfig.ignoreGhsas