Fix context logging methods to accept Any type per MCP spec

[Christian-Sidak]

Summary

Fixes #397

The MCP spec defines the logging notification data field as unknown (any JSON serializable type), but Context.log() and the convenience methods (debug, info, warning, error) only accepted str. This was inconsistent with both the spec and the existing ServerSession.send_log_message(data: Any) signature.

Changes:

• Changed parameter from message: str to data: Any in Context.log() and all convenience methods
• Removed the extra parameter, which was a workaround for the str-only limitation and caused confusion (calling with extra= kwargs raised TypeError since Context.log() did not accept them)
• Updated tests to cover structured data logging (dicts, lists, numbers, None)

Before (broken):

# Type error - spec says this should work
ctx.info({"event": "user_login", "user_id": 123})

After (fixed):

# All JSON serializable types now accepted
ctx.info("simple string message")
ctx.info({"event": "user_login", "user_id": 123})
ctx.debug(["step1", "step2", "step3"])
ctx.warning(42)

Backward compatible -- all existing code passing strings continues to work unchanged since the positional argument just changed name from message to data.

Test plan

• Existing test_context_logging passes (string messages)
• New test_context_logging_structured_data passes (dict, list, int, None)
• Updated test_logging_callback passes with new API

[Christian-Sidak]

Closing -- I see this has been actively worked on by several contributors (#400, #1907). Apologies for the duplicate!