Fix macOS CI: pin Python 3.12 for sonicscrewdriver virtualenv

[Copilot]

macOS-latest runners now default to Python 3.14, which has no available distributions for tensorflow or numpy==1.26.4, causing pythonInstall() to fail in CI.

Change

• R/reticulate-virtualenv.R: Pass python_version="3.12" to virtualenv_create() so the sonicscrewdriver virtualenv is always built against Python 3.12, the latest version supported by all required packages (tensorflow, numpy==1.26.4, scikit-maad, librosa, birdnetlib).

reticulate::virtualenv_create(envname = "sonicscrewdriver", packages = NULL, python_version = "3.12")

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.52%. Comparing base (583bf7b) to head (61fbefe).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #33   +/-   ##
=======================================
  Coverage   83.51%   83.52%           
=======================================
  Files          88       88           
  Lines        3058     3059    +1     
=======================================
+ Hits         2554     2555    +1     
  Misses        504      504           

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