🆕 Add SegFormer Architecture

[Jiaqi-Lv]

This pull request adds SegFormer segmentation model, and refactors the EfficientUNetTissueMaskModel to use shared utility modules for common layers.

New architectures for semantic segmentation

SegFormer
Mix Transformer (Encoder)

Refactoring for code reuse

• Refactors EfficientUNetTissueMaskModel to use the shared Conv2dReLU and SegmentationHead implementations from architecture.utils, replacing local definitions and reducing code duplication. [1] [2] [3] [4] [5]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.89%. Comparing base (445530f) to head (86c8e6a).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #1085    +/-   ##
=========================================
  Coverage    99.88%   99.89%            
=========================================
  Files           85       88     +3     
  Lines        11656    11962   +306     
  Branches      1531     1549    +18     
=========================================
+ Hits         11643    11949   +306     
  Misses           7        7            
  Partials         6        6            

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.