Fix nested sanitization of datetime and NaN values

[hownowstephen]

Summary

• _sanitize_value() only handled top-level dict values — datetime and NaN inside nested dicts or lists passed through unsanitized, causing TypeError during JSON serialization or silent data corruption
• Added recursion into dict and list types in _sanitize_value()
• 4 new tests covering nested dict, list, NaN, and deeply nested structures

Test plan

• Nested dict with datetime converts to timestamp
• List containing datetime values converts correctly
• Nested dict with NaN converts to None
• Deeply nested dict-in-list-in-dict handled
• All 52 tests pass

🤖 Generated with Claude Code

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Note

Low Risk
Low risk: limited to request payload sanitization, extending existing datetime/NaN handling to nested dicts/lists and backed by new unit tests.

Overview
Fixes payload sanitization so datetime and NaN values are converted even when nested inside dicts or lists before JSON requests are sent.

Adds recursive handling in ClientBase._sanitize_value() and extends the test suite with cases for nested dicts, lists, and deeply nested structures (plus minor test formatting cleanups).

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