chore: use frozendict on 3.15

[flying-sheep]

Not adding __lazy_imports__ yet, will do that once numba actually supports Python 3.15

• Release notes not necessary because: dev only change

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.25%. Comparing base (fabadb9) to head (a273eff).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #4287       +/-   ##
=========================================
+ Coverage      0   79.25%   +79.25%     
=========================================
  Files         0      128      +128     
  Lines         0    13462    +13462     
=========================================
+ Hits          0    10669    +10669     
- Misses        0     2793     +2793     

Flag	Coverage Δ
hatch-test.low-vers	77.48% <87.50%> (?)
hatch-test.pre	79.12% <100.00%> (?)

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

Files with missing lines	Coverage Δ
src/scanpy/experimental/pp/_normalization.py	94.68% <100.00%> (ø)
src/scanpy/experimental/pp/_recipes.py	100.00% <100.00%> (ø)
src/scanpy/neighbors/__init__.py	82.32% <100.00%> (ø)
src/scanpy/plotting/_v2/_core.py	30.55% <100.00%> (ø)
src/scanpy/plotting/legacy/_tools/paga.py	64.38% <100.00%> (ø)
src/scanpy/queries/_queries.py	46.26% <100.00%> (ø)
src/scanpy/tools/_louvain.py	100.00% <100.00%> (ø)
src/scanpy/tools/_sim.py	63.50% <100.00%> (ø)

... and 120 files with indirect coverage changes