Add CI/CD workflow for PR validation

.github/workflows/pr-checks.yml

@@ -0,0 +1,35 @@
+name: PR Checks
+
+on:
+  pull_request:
+    branches: [main, master]
+  push:
+    branches: [main, master]
+
+jobs:
+  validate:
+    name: Type Check, Build & Audit
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Type check
+        run: npm run typecheck
+
+      - name: Build
+        run: npm run build
+
+      - name: Security audit
+        run: npm audit --audit-level=high
+        continue-on-error: false