Clean up dependencies

- Move pytest, pytest-cov, pytest-xdist to dev dependencies
- Remove redundant jinja2 and uvicorn (included in fastapi[standard])
- Update CI to use --extra dev for test dependencies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/test.yml

@@ -16,6 +16,6 @@ jobs:
         with:
           version: "latest"
       - run: uv python install 3.13
-      - run: uv sync
+      - run: uv sync --extra dev
       - name: Run tests in parallel
         run: uv run pytest tests/ -n auto -v --tb=short