[manduinca]

Description Of Changes

I raise the minimum Python version to 3.12 in the package metadata, CI, and installation docs. I update the dependency minimums for the new CI jobs and remove the obsolete Matplotlib 3.7.0 test branch.

Validation on macOS arm64

• Python 3.12, exact minimum dependencies: 1,600 passed, 25 skipped, 1 xfailed (non-remote tests).
• Python 3.14 with CI dependency pins: non-remote tests passed with the required CI map data.
• Separate Python 3.12 installation without extras: 42 passed, 1 xfailed (packaging/units smoke tests).
• Built wheel: pip rejects Python 3.11 and accepts Python 3.12.

Checklist

• Closes Drop Python 3.11 #4149
• Fully documented