refactor: remove pint from models

[tlambert03]

this PR effectively undoes #37 and closes #70

while I love the concept of using pint to ensure that quantities and units are handled correctly, it does get annoying to deal with non built-in types throughout the pipeline, where it's not always clear whether you're getting a quantity (which requires special .magnitude handling in some cases). Leading to stuff like #70

I'm not dropping the dependency on pint yet, so it's still possible to use pint in functions calculating difficult stuff, like fluorophore photon emissions, for example, but there we would simply cast to/from quantities while doing the calculations, but not use them for model fields directly

[codecov]

Codecov Report

Attention: Patch coverage is 84.78261% with 7 lines in your changes missing coverage. Please review.

Project coverage is 84.19%. Comparing base (60445f9) to head (79b23e4).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/microsim/schema/spectrum.py	83.33%	3 Missing ⚠️
src/microsim/schema/simulation.py	0.00%	2 Missing ⚠️
src/microsim/psf.py	66.66%	1 Missing ⚠️
src/microsim/schema/_emission.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #71      +/-   ##
==========================================
- Coverage   84.49%   84.19%   -0.30%     
==========================================
  Files          49       49              
  Lines        2909     2892      -17     
==========================================
- Hits         2458     2435      -23     
- Misses        451      457       +6     

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[tlambert03]

this will be needed for #74 merging