Set up browser-based end-to-end testing using pytest-playwright:
- Add playwright-driver and pytest-playwright to nix flake
- Configure PLAYWRIGHT_BROWSERS_PATH for NixOS compatibility
- Create ServerHarness to manage live server for tests
- Add smoke tests for health endpoint and page loading
- Exclude e2e tests from pre-commit hook (require special setup)
Run e2e tests with: pytest tests/e2e/ -v -n 0
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
