- Fix JSON parsing bug: JavaScript FormData sends indicator list as
JSON string inside a list, now properly parsed on backend
- Move form event listener setup to _setupIndicatorForm() called from
addToCharts() so it's always attached regardless of indicator data
- Add immediate visual feedback: popup hides instantly on submit and
button shows "Updating..." text
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>