Fix CI: Install Node.js in containers for checkout action

ISSUE:
======
Gitea Actions containers need Node.js to run actions/checkout@v4
Error: 'exec: "node": executable file not found in $PATH'

FIX:
====
Added Node.js installation step before checkout in all jobs:

For Debian/Ubuntu containers (python:3.11-bullseye, ubuntu:22.04):
  apt-get update && apt-get install -y curl git
  curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
  apt-get install -y nodejs

For Alpine containers (gitleaks, trivy):
  apk add --no-cache nodejs npm curl git

JOBS FIXED:
===========
✅ lint-and-test
✅ secret-scanning
✅ security-scan
✅ dependency-scan
✅ sast-scan
✅ container-scan
✅ docker-build-test (no container, already works)

This is a common requirement for Gitea Actions when using
custom containers.

.github/workflows/ci.yml

@@ -27,6 +27,12 @@ jobs:
           --health-retries 5
 
     steps:
+      - name: Install Node.js for checkout action
+        run: |
+          apt-get update && apt-get install -y curl git
+          curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
+          apt-get install -y nodejs
+
       - name: Check out code
         uses: actions/checkout@v4
 
@@ -94,6 +100,12 @@ jobs:
     container:
       image: python:3.11-bullseye
     steps:
+      - name: Install Node.js for checkout action
+        run: |
+          apt-get update && apt-get install -y curl git
+          curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
+          apt-get install -y nodejs
+
       - name: Check out code
         uses: actions/checkout@v4