BDMS-626: mp height fixes

[jacob-a-brown]

Why

This PR addresses the following problem / context:

• measuring_point_height for both the MeasurementPointHistory and Observation tables should be set to the same value for well inventory
• null mp heights should be allowed

How

Implementation summary - the following was changed / added / removed:

• remove the requirement for mp heights
• add test to ensure null values are allowed

Notes

Any special considerations, workarounds, or follow-up work to note?

• Use bullet points here

[Copilot]

Pull request overview

This PR updates the well inventory CSV import flow to allow measuring_point_height to be omitted (NULL), including when a non-null depth_to_water_ft (observation value) is provided, while keeping the “universal MP height” behavior consistent across well (MeasuringPointHistory/Thing property) and Observation.

Changes:

• Removed the import-time validation that rejected rows where depth_to_water_ft was present but both MP height fields were blank.
• Updated/added a test to confirm blank MP heights are accepted when depth_to_water_ft is provided, and removed the now-obsolete failure test.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
services/well_inventory_csv.py	Drops the “MP height required when depth-to-water present” guard to allow NULL MP heights during import.
tests/test_well_inventory.py	Reworks tests to assert NULL MP heights are permitted with non-null observations and removes the prior error expectation.

[ksmuczynski]

Looks good!