Add CI workflow for backend, frontend, and Docker builds

.github/workflows/ci.yml

@@ -0,0 +1,66 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./backend
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.14.3"
+          cache: "pip"
+          cache-dependency-path: backend/requirements.txt
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+
+      - name: Run tests (if present)
+        run: |
+          if [ -f api/tests.py ] || [ -d api/tests ]; then
+            python manage.py test
+          else
+            echo "No backend tests found in api/; skipping test step."
+          fi
+
+  frontend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./frontend
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: "npm"
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Build
+        run: npm run build
+  docker-build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build Docker images
+        run: docker compose build