Move copy-webpack-plugin to devDependencies

[franco-zalamena-iterable]

Summary

• Move copy-webpack-plugin from dependencies to devDependencies
• It is only used in webpack.dev.config.js during development

Test plan

• Verify dev build still works
• Verify production build still works

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.45%. Comparing base (190a168) to head (e049325).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #565   +/-   ##
=======================================
  Coverage   74.45%   74.45%           
=======================================
  Files          57       57           
  Lines        2736     2736           
  Branches      798      814   +16     
=======================================
  Hits         2037     2037           
+ Misses        698      658   -40     
- Partials        1       41   +40     

☔ View full report in Codecov by Sentry.
📢 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.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.