Fix starlette dependency for Python 3.9 compatibility

Starlette 0.30.0+ requires Python >= 3.10. Add environment markers
to pin starlette < 0.30.0 for Python 3.9 while allowing latest for
3.10+.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: deborahjacob-botanu

pyproject.toml

@@ -132,7 +132,8 @@ dev = [
     "pytest-cov >= 4.1.0",
     "coverage[toml] >= 7.0",
     "httpx >= 0.24.0",
-    "starlette >= 0.27.0",
+    "starlette >= 0.27.0, < 0.30.0; python_version < '3.10'",
+    "starlette >= 0.27.0; python_version >= '3.10'",
     "ruff >= 0.4.0",
     "mypy >= 1.7.0",
     "pre-commit >= 3.5.0",