fix: preserve Settings Editor TOC section state across focus changes (fixes PlatformNetwork/bounty-challenge#21908)

[echobt]

Fix for PlatformNetwork/bounty-challenge#21908: Settings Editor loses TOC section state on focus change

Changes

• Moved the active TOC section state to a module-level signal (outside the component)
• Added localStorage persistence via safeGetItem/safeSetItem so the selected section survives component unmount/remount cycles
• The section state is now preserved when switching between editor tabs and returning to settings

Files Modified

• src/components/settings/SettingsEditor.tsx

[echobt]

Closing: this fix has already been applied directly to the main branch. The branch is based on an older commit and merging it would regress other fixes. The referenced issue is resolved on main.