feat(ci): add backend CI job with common-plat checkout, upgrade Node to 22

- Backend: common-plat checkout, pnpm build, typecheck, 135 tests
- Web: upgrade Node 20→22, add concurrency group

.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: CI — Lint, Typecheck, Test
+name: CI
 
 on:
   push:
@@ -6,19 +6,64 @@ on:
   pull_request:
     branches: [main]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
-  ci:
+  backend:
+    name: Backend — typecheck + test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Checkout common-plat (for @bytelyst/* packages)
+        uses: actions/checkout@v4
+        with:
+          repository: saravanakumardb1/learning_ai_common_plat
+          path: learning_ai_common_plat
+          token: ${{ secrets.GH_PAT }}
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Install pnpm (for common-plat build)
+        run: npm install -g pnpm
+
+      - name: Build @bytelyst/* packages
+        working-directory: learning_ai_common_plat
+        run: |
+          pnpm install --frozen-lockfile
+          pnpm build
+
+      - name: Install backend dependencies
+        working-directory: backend
+        run: npm ci
+
+      - name: Backend typecheck
+        working-directory: backend
+        run: npm run typecheck
+
+      - name: Backend tests
+        working-directory: backend
+        run: npm test
+        env:
+          DB_PROVIDER: memory
+          JWT_SECRET: ci-test-secret-at-least-32-characters-long
+
+  web:
+    name: Web — typecheck + lint + test
     runs-on: ubuntu-latest
     defaults:
       run:
         working-directory: web
-
     steps:
       - uses: actions/checkout@v4
 
       - uses: actions/setup-node@v4
         with:
-          node-version: 20
+          node-version: 22
           cache: npm
           cache-dependency-path: web/package-lock.json