ci: Add PR workflow to check install, lint, and build

Runs npm ci + lint + next build on every pull request (and via manual
dispatch) so broken builds are caught before merge.

Author: TamimEhsan

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI
+
+# Verify the project installs, lints, and builds on every pull request.
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Lint
+        run: npm run lint
+
+      - name: Build
+        run: npm run build