fix ruff errors and remove isort and black

[m-reuter]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 12.28070% with 50 lines in your changes missing coverage. Please review.

Project coverage is 34.89%. Comparing base (3f1d94e) to head (8454986).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
lapy/_tria_io.py	9.52%	19 Missing ⚠️
lapy/diffgeo.py	0.00%	12 Missing ⚠️
lapy/io.py	0.00%	7 Missing ⚠️
lapy/_tet_io.py	20.00%	4 Missing ⚠️
lapy/_read_geometry.py	0.00%	3 Missing ⚠️
lapy/plot.py	0.00%	3 Missing ⚠️
lapy/conformal.py	0.00%	1 Missing ⚠️
lapy/tria_mesh.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #65   +/-   ##
=======================================
  Coverage   34.89%   34.89%           
=======================================
  Files          14       14           
  Lines        2367     2367           
  Branches      299      299           
=======================================
  Hits          826      826           
  Misses       1457     1457           
  Partials       84       84           

Flag	Coverage Δ
unittests	34.89% <12.28%> (ø)

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