fix(container): Command-Line Container build fails — PETSc 3.21/3.22 API mismatch

[jcgraciosa]

Summary

The GHCR: Command-Line Container build has been failing since PR #242
(2026-06-18), which added UW_DMPlexComputeResidualByKeyVolumeOnly to
petsc_compat.h using APIs not present in PETSc 3.21.5:

• DMCopyFields with 4 args (3.21 only has 2)
• DMPlexComputeResidualByKey (not present in 3.21)

Both are available from PETSc 3.24 onwards (verified against conda-forge).

Fix

Bump environment.yaml from petsc=3.21.5 / petsc4py=3.21.5 to
petsc=3.24 / petsc4py=3.24.

This only affects the container — regular developers use pixi, not
environment.yaml.