[Hotfix Main]: [SNAPPY] Custom logic to calculate min_vol quality metric

[github-actions]

Hotfix of PR #1788 (#1788) to the main branch.
Hey @piotrkluba, please review this hotfix PR created from your original PR.

---

Note

Medium Risk
Changes default mesh-quality thresholds (minVol) based on refinement settings, which can alter meshing behavior and outputs for existing Snappy workflows even when users did not explicitly configure this metric.

Overview
QualityMetrics.min_pyramid_cell_volume (min_vol) is changed from a fixed default to an optional field: when omitted it now derives meshQuality.minVol as 1e-10 * (effective_min_spacing^3), while still supporting explicit values and False (translated to -1e30).

The Snappy translator adds logic to compute effective_min_spacing by taking the minimum across surface defaults, body/region min_spacing and proximity_spacing, edge spacings, and projected volume UniformRefinements, then snapping it down to the octree spacing series. Golden JSON fixtures and translator tests are updated (including relaxed atol) to match the new computed minVol outputs.

^{Written by Cursor Bugbot for commit a547edc. This will update automatically on new commits. Configure here.}