Combinator builder frontend

[ziaddevv]

Adds the frontend create/edit flow for Combinator selections.

Summary:

• Adds a Combinator builder page for selecting include/exclude builders.
• Supports union/intersection operations for each group.
• Wires Combinator routes and navigation.
• Adds frontend validation
• Adds Cypress coverage for create, edit, validation, error states, and My Selections navigation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.50%. Comparing base (41f25e8) to head (4f20201).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1186   +/-   ##
=======================================
  Coverage   92.50%   92.50%           
=======================================
  Files          78       78           
  Lines        4711     4711           
=======================================
  Hits         4358     4358           
  Misses        353      353           

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[audiodude]

This looks really good! I think the main thing from an architecture perspective is thinking through when helper methods in the component make sense, versus when they're distracting. Not every @click handler needs to use a helper, but that also doesn't mean that none of them should!

[ziaddevv]

I rebased the branch onto latest origin/main,removed Combinator from the nav for now and renamed the loading flag to buildersFetchFinished.