Drop py3.9 fix ci

[janfb]

Given that we have #1406 and now the new pymc release drops python3.9 support, I suggest we also drop Python 3.9 (End of Life was October 2024).

This PR updates the docs about our Python Version and switches to uv throughout the CI.

Switching ruff to be run on 3.10 also comes with new best practices, which could all be auto-fixed and are added in a separat commit.

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.38%. Comparing base (69b7f38) to head (bc2dbbd).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sbi/samplers/vi/vi_divergence_optimizers.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1412      +/-   ##
==========================================
+ Coverage   89.27%   89.38%   +0.11%     
==========================================
  Files         119      119              
  Lines        8905     8905              
==========================================
+ Hits         7950     7960      +10     
+ Misses        955      945      -10     

Flag	Coverage Δ
unittests	89.38% <92.30%> (+0.11%)	⬆️

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

Files with missing lines	Coverage Δ
sbi/analysis/plot.py	84.71% <100.00%> (-0.14%)	⬇️
sbi/diagnostics/sbc.py	92.95% <100.00%> (ø)
sbi/neural_nets/factory.py	90.90% <ø> (ø)
sbi/samplers/mcmc/slice_numpy.py	92.05% <ø> (ø)
sbi/simulators/simutils.py	100.00% <ø> (ø)
sbi/utils/conditional_density_utils.py	94.55% <ø> (ø)
sbi/utils/diagnostics_utils.py	100.00% <ø> (ø)
sbi/utils/sbiutils.py	86.79% <ø> (ø)
sbi/utils/simulation_utils.py	100.00% <ø> (ø)
sbi/samplers/vi/vi_divergence_optimizers.py	86.64% <50.00%> (ø)

... and 5 files with indirect coverage changes

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[michaeldeistler]

Thank you!

[janfb]

all checks are passing, see duplicate #1417