fix: pkgs via npm, not CDN; alt-drag for zoom

[jennifer-richards]

Install chart.js and other JS dependencies via npm so they can be bundled.

Noticed that the drag + pan config for the stats graphs interacted badly, so added "alt" modifier to the drag-to-zoom action.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.48%. Comparing base (7f25c28) to head (5a918ae).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10795      +/-   ##
==========================================
- Coverage   88.49%   88.48%   -0.02%     
==========================================
  Files         332      332              
  Lines       44838    44838              
==========================================
- Hits        39679    39673       -6     
- Misses       5159     5165       +6     

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