Add GitHub Actions CI workflow

Runs pytest (backend) and npm build (frontend) on every push and PR to main.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ppradyoth

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: backend
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install backend dependencies
+        run: pip install -r requirements.txt
+
+      - name: Run backend tests
+        env:
+          ENABLE_AI_FALLBACK: "true"
+        run: pytest
+
+  frontend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: frontend
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install frontend dependencies
+        run: npm install
+
+      - name: Build frontend
+        run: npm run build
+