v1.1.3

Fix macOS blank terminals — node-pty spawn-helper was not executable on Darwin.

The prebuilt spawn-helper binary in node-pty/prebuilds/darwin-* was missing the executable permission bit, causing posix_spawn() to fail with EACCES on macOS. All terminal PTY sessions silently failed to spawn, leaving terminals blank.

Added a postinstall script in packages/backend/package.json to auto-fix permissions after any future npm install.