Fix CP2K 2025 stress parsing in bar

[SchrodingersCattt]

Summary

• accept analytical stress tensor headers in both GPa and bar
• normalize bar values to GPa in the block parser before the existing dpdata virial conversion
• add a regression test showing equivalent GPa and bar tensors produce identical parsed values

Why

CP2K 2025.x may print STRESS| Analytical stress tensor [bar]. The previous GPa-only regex did not match that block, so cp2kdata/e_f silently omitted virials while retaining the other labels.

Tests

pytest -q tests/test_stress.py tests/test_energy_force/test_energy_force.py tests/test_dpdata/test_labeledsys.py
260 passed

Fixes #99. Related to #98.