[grade=B] DC-070: Add CI/CD pipeline — GitHub Actions workflow

Runs on push/PR to main: npm ci → ESLint (no warnings) → Jest with coverage → upload artifact.
Uses permissions: contents: read for supply-chain hardening.
Node 20 matches package.json engine requirement.

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+          cache-dependency-path: dashcaddy-api/package-lock.json
+
+      - name: Install dependencies
+        working-directory: dashcaddy-api
+        run: npm ci
+
+      - name: Run ESLint
+        working-directory: dashcaddy-api
+        run: npx eslint . --max-warnings 0
+
+      - name: Run tests with coverage
+        working-directory: dashcaddy-api
+        run: npx jest --coverage --ci --coverageReporters=text --coverageReporters=text-lcov
+
+      - name: Upload coverage report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: dashcaddy-api/coverage/