4.0.5

Remove Zscaler/corporate proxy configuration from updater

Simplifies the auto-updater by removing:
- All Zscaler detection and certificate handling
- Corporate proxy configuration and authentication
- ZIP fallback download mechanism
- PowerShell/curl download alternatives
- SSL/TLS bypass switches
- Certificate management IPC handlers

The updater now uses standard electron-updater with delta updates,
silent install, and scheduled checks.