Implement Open Source edition limits and feature restrictions

- Add 5 mutation types (paraphrase, noise, tone_shift, prompt_injection, custom)
- Cap mutations at 50 per test run
- Force sequential execution only
- Disable GitHub Actions integration (Cloud feature)
- Add upgrade prompts throughout CLI
- Update README with feature comparison
- Add limits.py module for centralized limit management
- Add cloud and limits CLI commands
- Update all documentation with Cloud upgrade messaging

rust/Cargo.toml

@@ -14,4 +14,3 @@ pyo3.workspace = true
 rayon.workspace = true
 serde.workspace = true
 serde_json.workspace = true
-