feat: address PR review feedback with improved dependency constraints and tests

- Add upper bound to litellm constraint: litellm>=1.72.0,<2.0.0
- Enhance test suite with parameterized testing across multiple model types
- Add version constraint validation test to ensure proper bounds
- Improve test documentation with detailed explanations
- Add error handling enhancements as suggested in review

Addresses feedback from PR review by joaomdmoura in #3006

Co-Authored-By: João <joao@crewai.com>

pyproject.toml

@@ -21,7 +21,7 @@ dependencies = [
     "jsonref>=1.1.0",
     "json-repair>=0.25.2",
     "auth0-python>=4.7.1",
-    "litellm>=1.72.0",
+    "litellm>=1.72.0,<2.0.0",
     "pyvis>=0.3.2",
     "uv>=0.4.25",
     "tomli-w>=1.1.0",