Fix spectra scaling and url loading

[tlambert03]

this fixes a number of issues in the spectra viewer that were introduced in the upgrade to react 19 and apollo client 3 in #272

it also adds a significant number of javascript tests to hopefully prevent regressions in the future

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.11%. Comparing base (7cda4a6) to head (d4d6795).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #296   +/-   ##
=======================================
  Coverage   58.11%   58.11%           
=======================================
  Files         103      103           
  Lines        8359     8359           
=======================================
  Hits         4858     4858           
  Misses       3501     3501           

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