chore(deps): upgrade to langgraph-checkpoint 3.0 and redisvl 0.11

- Upgrade langgraph-checkpoint from >=2.0.21,<3.0.0 to >=3.0.0,<4.0.0
- Upgrade redisvl from >=0.5.1,<1.0.0 to >=0.11.0,<1.0.0
- Update Python requirement from >=3.9,<3.14 to >=3.10,<3.14 (Python 3.9 EOL)
- Remove Python 3.9 from classifiers
- Update Black target-version to remove py39

BREAKING CHANGE: Drops Python 3.9 support, now requires Python 3.10+

Addresses security vulnerability CVE-2025-64439 in langgraph-checkpoint

Author: bsbodden