Add Gitea CI workflow; fix ruff lint issues

.gitea/workflows/test.yml

@@ -0,0 +1,30 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.13"
+
+      - name: Install dependencies
+        run: |
+          pip install ruff
+          pip install -r requirements.txt
+
+      - name: Lint
+        run: ruff check .
+
+      - name: Run tests
+        run: pytest tests/ -v