feat: add seg_contact layer for storing segment contact data

[supersergiy]

Summary

• Add volumetric layer implementation for segment contacts
• Contact data structure with face coordinates and affinities
• Binary file backend with chunked storage
• Info spec for layer configuration
• Build functions for layer construction
• Support for pointcloud generation from mesh data

Test plan

• Tests will be added in a follow-up PR

[codecov]

Codecov Report

❌ Patch coverage is 0% with 525 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.41%. Comparing base (a66a409) to head (336e000).

Files with missing lines	Patch %	Lines
...etta_utils/layer/volumetric/seg_contact/backend.py	0.00%	297 Missing ⚠️
...ta_utils/layer/volumetric/seg_contact/info_spec.py	0.00%	128 Missing ⚠️
zetta_utils/layer/volumetric/seg_contact/build.py	0.00%	40 Missing ⚠️
...etta_utils/layer/volumetric/seg_contact/contact.py	0.00%	30 Missing ⚠️
zetta_utils/layer/volumetric/seg_contact/layer.py	0.00%	25 Missing ⚠️
...tta_utils/layer/volumetric/seg_contact/__init__.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1122      +/-   ##
==========================================
- Coverage   99.97%   94.41%   -5.57%     
==========================================
  Files         180      186       +6     
  Lines        8912     9437     +525     
==========================================
  Hits         8910     8910              
- Misses          2      527     +525     

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