[python] Fix and test SpatialData transformation exporter

[jp-dark]

Fixes:

• Fix changes from SOMA coordinate axis names to SpatialData coordinate dimension names.
• Invert SOMA scene-to-points transform to correctly store SpatialData point-to-scene transformation.
• Fix type annotation for GeoPandas GeoDataFrame.

Clean-up:

• Import spatialdata as sd.
• Add tests for converting transformations.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.38%. Comparing base (946d3f7) to head (4ecda24).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3330      +/-   ##
==========================================
+ Coverage   85.14%   85.38%   +0.23%     
==========================================
  Files          53       53              
  Lines        5568     5568              
==========================================
+ Hits         4741     4754      +13     
+ Misses        827      814      -13     

Flag	Coverage Δ
python	85.38% <100.00%> (+0.23%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
python_api	85.38% <100.00%> (+0.23%)	⬆️
libtiledbsoma	∅ <ø> (∅)

---- 🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[jp-dark]

Fix to sc-57972