Move installer.nsh to frontend directory and update to version 1.6.2 - Fix...

Move installer.nsh to frontend directory and update to version 1.6.2 - Fix GitLab CI build issue by moving installer.nsh from ignored build/ directory to tracked frontend/ directory - Update package.json to reference installer.nsh in frontend directory - Fix changelog JSON syntax error - Version 1.6.2 with cleanup fixes and installer improvements