add CI workflow for running server tests

.github/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI — Run server tests
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  test-server:
+    name: Run Python tests (server)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.11"
+
+      - name: Cache pip
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('server/requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+
+      - name: Install server dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r server/requirements.txt
+
+      - name: Run server tests
+        working-directory: server
+        env:
+          PYTHONDONTWRITEBYTECODE: 1
+        run: |
+          pytest -q