Update main Python version to 3.13

[greschd]

Currently blocked by sphinx-doc/sphinx#13178.

We could presumably fix that by upgrading to Sphinx 8.2.0, but that would require dropping Python 3.10 support on the doc build.
Alternatively, we could ignore the resulting warning.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.83%. Comparing base (d410c1a) to head (5687f4c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #841      +/-   ##
==========================================
- Coverage   94.97%   94.83%   -0.14%     
==========================================
  Files         110      110              
  Lines        5773     5773              
  Branches      296      296              
==========================================
- Hits         5483     5475       -8     
- Misses        289      297       +8     
  Partials        1        1              

Flag	Coverage Δ
direct-launch	92.20% <ø> (ø)
minimum-deps	93.07% <ø> (ø)
python-3.10	94.16% <ø> (ø)
python-3.11	94.09% <ø> (ø)
python-3.12	94.09% <ø> (ø)
python-3.13	94.19% <ø> (-0.14%)	⬇️
server-2024R2SP5	?
server-2025R1SP4	94.12% <ø> (ø)
server-2025R2SP2	94.09% <ø> (ø)
server-2026R1	94.09% <ø> (ø)
server-latest	94.73% <ø> (ø)

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