TEST: Add getBoundingBox regression tests for node geometries and ImageGeom

[jmarquisbq]

Summary

Adds the regression unit tests that should have accompanied the bounding-box
fix in commit a31beeb / #1649 (BUG: Fix INodeGeometry0D::getBoundingBox upper-corner initialization).

That fix corrected INodeGeometry0D::getBoundingBox(), which had seeded the
upper corner with std::numeric_limits<float>::min() — the smallest positive
normal float (~1.18e-38) — instead of std::numeric_limits<float>::lowest().
For any node geometry whose maximum coordinate on an axis was <= ~0 (e.g. a
mesh centered at or below the origin), the max corner never updated during the
vertex walk, producing a wrong/oversized bounding box. Geometries lying entirely
in positive space happened to work, which masked the bug. The fix shipped
without any test coverage, so this PR closes that gap.

Changes

All changes are in test/GeometryTest.cpp:

• testNodeGeometryBoundingBox<>() — a templated helper that exercises three
  coordinate regimes against the shared INodeGeometry0D::getBoundingBox():
  • negative space — the BUG: Fix INodeGeometry0D::getBoundingBox upper-corner initialization #1649 regression (fails without the fix),
  • origin-straddling — mixed-sign coordinates plus an exact-zero vertex,
  • positive space — guards against an over-correction breaking the common case.
• TEST_CASE("Node geometry getBoundingBox handles negative coordinates") —
  runs the helper against every node geometry that inherits the method:
  VertexGeom, EdgeGeom, TriangleGeom, QuadGeom, TetrahedralGeom,
  HexahedralGeom.
• TEST_CASE("ImageGeom getBoundingBox handles a negative origin") — the
  related grid geometry, which has its own independent implementation. Verifies
  both getBoundingBox() (float64) and getBoundingBoxf() (float32) with a
  negative origin (max-Y lands exactly on 0, the boundary case).

RectGridGeom has no getBoundingBox() of its own, so it needs no coverage here.

Verification

• Confirmed the negative-space case fails against the pre-a31beeb code
  (getMaxPoint() returns ~0 instead of the least-negative coordinate) and
  passes with the fix in place.
• Full GeometryTest.cpp suite passes: 270 assertions across 14 test cases.

Unit Testing

• Unit test covering correct output (bounding box of node + image geometries
  across negative / origin-straddling / positive coordinate ranges)
• Unit test for invalid input code paths — n/a (no new filter/error paths;
  this covers a geometry accessor)

Code Cleanup

• No commented out code
• No API changes were made
• No major design changes were made
• Added test (or behavior not changed)
• Updated API documentation (or API not changed) — n/a
• Added license to new files (if any) — n/a, no new files
• Added example pipelines that use the filter — n/a
• Classes and methods are properly documented