dankinstall: enable dms.service instead of wanting it from hyprland-session.target

[Pedroj-64]

Fixes #3465

On Hyprland, dankinstall ran systemctl --user add-wants hyprland-session.target dms. hyprland-session.target is Before=graphical-session.target and dms.service is After=graphical-session.target, and systemd orders a target after the units it wants. That closes a cycle:

dms.service/start after graphical-session.target/verify-active after hyprland-session.target/start after dms.service

systemd breaks it by dropping the start job, so dms never autostarts (enabled, inactive in dms doctor).

dms.service already has WantedBy=graphical-session.target, so the Hyprland path now just runs systemctl --user enable dms.service.

The test puts a fake systemctl on PATH and checks the arguments; it fails on the old code.

Users who already ran the installer keep the old symlink and need to rm ~/.config/systemd/user/hyprland-session.target.wants/dms.service and re-enable. I left that out to keep this small.

[bbedward]

507b818