Use 'uv sync' instead of 'uv pip install' (install what's in uv.lock)

and adapt the cache key accordingly

.github/workflows/pytest.yml

@@ -58,7 +58,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: .venv
-          key: uv-venv-${{ runner.os }}-${{ matrix.python-version }}-${{ hashFiles('uv.lock') }}
+          key: uv-venv-${{ runner.os }}-${{ matrix.python-version }}-lock-${{ hashFiles('uv.lock') }}
       - name: Create virtual environment
         shell: bash
         run: |
@@ -67,7 +67,7 @@ jobs:
           fi
       - name: Install Python environment
         shell: bash
-        run: uv pip install -e ".[dev]"
+        run: uv sync --extra dev --locked
       - name: List Python dependencies
         shell: bash
         run: uv pip list