fix: remove unnecessary system pip install from lint job

Ruff runs via uvx in its own isolated environment and does not need
the project's runtime dependencies installed. This avoids PEP 668
externally-managed-environment errors on Debian-based runners.

.gitea/workflows/ci.yml

@@ -24,12 +24,6 @@ jobs:
       - name: Set up uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh && echo "$HOME/.local/bin" >> $GITHUB_PATH
 
-      - name: Set up Python
-        run: uv python install 3.13
-
-      - name: Install dependencies
-        run: uv pip install --system -r requirements.txt ruff
-
       - name: Run ruff check
         run: uvx ruff check .