Add app rail hover expansion setting

[ZacharyZcR]

Summary

• add a sidebar preference to disable app rail hover expansion
• keep the existing pin-open behavior intact and default hover expansion on for existing users
• sync the new preference through cloud user settings and migrate existing databases safely

Verification

• npx prettier --check .
• npx tsc --noEmit
• npm run lint
• npm run build
• git diff --check

Fixes Termix-SSH/Support#887

[LukeGus]

LGTM, thanks