Fix CI: use venv to avoid PEP 668 externally-managed-environment error

.gitea/workflows/ci.yml

@@ -18,20 +18,28 @@ jobs:
 
       - name: Set up Python
         run: |
-          apt-get update && apt-get install -y python3 python3-pip python3-venv || true
+          apt-get update && apt-get install -y python3 python3-venv || true
           python3 --version
 
       - name: Install dependencies
         run: |
-          python3 -m pip install --upgrade pip
+          python3 -m venv .venv
-          python3 -m pip install -r requirements.txt
+          source .venv/bin/activate
-          python3 -m pip install -r requirements-dev.txt
+          pip install --upgrade pip
+          pip install -r requirements.txt
+          pip install -r requirements-dev.txt
 
       - name: Lint with ruff
-        run: python3 -m ruff check .
+        run: |
+          source .venv/bin/activate
+          ruff check .
 
       - name: Format check with ruff
-        run: python3 -m ruff format --check .
+        run: |
+          source .venv/bin/activate
+          ruff format --check .
 
       - name: Run tests
-        run: python3 -m pytest -q
+        run: |
+          source .venv/bin/activate
+          pytest -q