feat: NVIDIA fix for gaming mode (kernel parameters and early modules)

Untested on hardware; .no-release-yet keeps it out of the release.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

lib/login-manager.sh

@@ -109,6 +109,7 @@ gaming_enable() {
     esac
     create_desktop_shortcut
     steam_enable
+    nvidia_enable || return 1
     os_name_enable || return 1
 }
 
@@ -124,6 +125,7 @@ gaming_disable() {
     steam_disable
     krevert gaming
     os_name_disable
+    nvidia_disable
     ok "The PC boots to the normal login screen again (from the next boot)."
 }