Bugfix: Fix NetCDF CF convention support to read Stage IV precipitation files

[JohnHalleyGotway]

Describe the Problem

Stage IV precipitation data is available publicly from a few different sources, for different regions and accumulation intervals, and in different file formats.

The NCAR GDEX record d507005 provides it in GRIB2 format, with the data lagging approx 1 month behind. It contains files for 1, 6, and 24 hour accumulations. That data is useful for retrospective studies. And MET processes this data just fine.

NOAA also now provides StageIV data in a CF-compliant NetCDF format, described at https://water.noaa.gov/about/precipitation-data-access. However, MET errors out when attempting to read this data.

Expected Behavior

This issue is to fix MET's support of the NetCDF CF convention so that it can parse these NetCDF Stage IV dataset without error.

To Reproduce

Describe the steps to reproduce the behavior:

> wget https://water.noaa.gov/resources/downloads/precip/stageIV/2026/01/13/nws_precip_1day_20260113_conus.nc
> met-12.2.0/bin/plot_data_plane nws_precip_1day_20260113_conus.nc st4.ps 'name="observation"; level="(*,*)";'
WARNING: NcCfFile::get_grid_mapping_polar_stereographic() -> The X coordinates (Meter) must be in meters or kilometers for MET.
ERROR  : NcCfFile::update_grid(Grid &) -> Grid is not ready

I'll note that changing the units from Meter to meter does indeed enable MET to read the data, although other problems are revealed by the resulting plot:

met-12.2.0/bin/plot_data_plane nws_precip_1day_20260113_conus_PATCH.nc plot.ps 'name="observation"; level="(*,*)";'

Replotting with the range (0, 5) improves things slightly:

met-12.2.0/bin/plot_data_plane nws_precip_1day_20260113_conus_PATCH.nc plot.ps 'name="observation"; level="(*,*)";' -plot_range 0 5

Here are 3 issues:

1. Update the MET library code to make unit checking case-insensitive.
2. Clearly the grid is upside down in MET. That should be fixed.
3. For some reason, there are spurious values of -10000 over Canada. But that's likely a data problem and not a software problem.

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