Preserve JSON-like string parameters

[adsharma]

Fixes: LadybugDB/ladybug#580

Summary

• stop pybind parameter binding from auto-parsing strings that look like JSON
• add a regression test for JSON-like strings stored in STRING columns

Root cause

The pybind parameter conversion path parsed Python strings starting with { or [ as JSON, which changed plain str parameters into nested values before assignment. When coerced back to STRING, JSON spelling and nulls were not preserved.

Validation

• make build-pybind-subdir LBUG_SOURCE_DIR=../ladybug
• uv run pytest test/test_parameter.py::test_json_like_string_param_round_trips_as_string -q
• uv run pytest -q
• LBUG_PYTHON_BACKEND=capi uv run pytest test/test_parameter.py::test_json_like_string_param_round_trips_as_string -q