feat(schema): add mpp/image_width/image_height/magnification catalog columns

[timtreis]

Adds four additive columns to the shared catalog contract (_catalog_schema.CATALOG_COLUMNS) for H&E image resolution: mpp (Float64), image_width/image_height (Int64), magnification (string). RANGE_COLUMNS auto-derives, so mpp/dims become range-queryable.

Part of the H&E detection + image-resolution metadata feature (engine + web PRs follow). Merge this first — the engine rev-bumps its sddb pin to this commit (unknown columns are already allowed by validate(), so this is non-breaking on its own).

28/28 tests pass.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.91%. Comparing base (975a0ff) to head (a6789d7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #19   +/-   ##
=======================================
  Coverage   91.91%   91.91%           
=======================================
  Files          19       19           
  Lines        1460     1460           
=======================================
  Hits         1342     1342           
  Misses        118      118           

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