build(ci): use uv for Python package management

Replace manual venv creation and pip with uv, a fast Python package
installer and resolver written in Rust.

Benefits:
- Significantly faster package installation
- Built-in caching support
- Better dependency resolution
- More reliable in CI environments

Changes:
- Add astral-sh/setup-uv@v4 action
- Replace venv + pip with uv venv + uv pip install
- Enable uv caching for faster CI runs

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: aepfli

.github/workflows/ci.yml

@@ -123,20 +123,21 @@ jobs:
         with:
           python-version: '3.10'
 
-      - name: Create virtualenv
-        run: python -m venv .venv
-
-      - name: Install maturin and pytest
-        run: |
-          source .venv/bin/activate
-          pip install maturin pytest
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+        with:
+          enable-cache: true
 
-      - name: Build Python package
+      - name: Install dependencies and build package
         run: |
+          cd python
+          uv venv
+          uv pip install maturin pytest
           source .venv/bin/activate
-          cd python && maturin develop
+          maturin develop
 
       - name: Run Python tests
         run: |
+          cd python
           source .venv/bin/activate
-          cd python && pytest tests/ -v
+          pytest tests/ -v