Fix #289: Add ShortestWeightConstrainedPath model

[zazabap]

Summary

• Add ShortestWeightConstrainedPath satisfaction problem model (bicriteria s-t path with length and weight bounds)
• Register in CLI dispatch, aliases, and create command
• Unit tests with brute-force solver verification
• Paper documentation

Fixes #289

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.61%. Comparing base (d309549) to head (3029f12).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #632   +/-   ##
=======================================
  Coverage   96.61%   96.61%           
=======================================
  Files         218      218           
  Lines       29352    29352           
=======================================
  Hits        28357    28357           
  Misses        995      995           

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