Add pytest suite and CI test gate

.gitea/workflows/docker.yml

@@ -9,7 +9,41 @@ on:
   workflow_dispatch:
 
 jobs:
+  test:
+    runs-on: ubuntu-latest
+    services:
+      mariadb:
+        image: mariadb:11
+        env:
+          MARIADB_DATABASE: jellomator_test
+          MARIADB_USER: jellomator
+          MARIADB_PASSWORD: jellomator
+          MARIADB_ROOT_PASSWORD: root
+        ports:
+          - 3306:3306
+        options: >-
+          --health-cmd="mariadb-admin ping -h 127.0.0.1 -uroot -proot"
+          --health-interval=5s
+          --health-timeout=5s
+          --health-retries=20
+    env:
+      DB_HOST: 127.0.0.1
+      DB_PORT: "3306"
+      DB_USER: jellomator
+      DB_PASSWORD: jellomator
+      DB_NAME: jellomator_test
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - name: Install Python dependencies
+        run: pip install -r backend/requirements-dev.txt
+      - name: Run backend tests
+        run: pytest -q
+
   build-and-push:
+    needs: test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4