feat(terra): replace tuigreet with a quickshell greeter

greetd now runs a throwaway Hyprland hosting dotfiles/quickshell/greeter.qml,
configured per host via homelab.greeter.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

dotfiles/quickshell/CLAUDE.md

@@ -100,6 +100,8 @@ on it, hence the index loops in `HyprChromeShell`.
   and its panels, with `Bar/Panels/BarPanel.qml` the chamfered chrome they all
   extend; `Widgets/Polkit/` is the authentication agent and its dialog;
   `Widgets/Launcher/` is the primary application launcher (`SUPER_L`);
+  `Widgets/Greeter/` is the greetd login screen, run standalone via `greeter.qml`
+  (see `services/desktop/quickshell-greeter.nix`), NOT part of `shell.qml`;
   `Theme/Theme.qml` is this tree's palette singleton. `DebugWindow.qml` stages a
   single widget on the secondary monitor for eyeballing it in isolation.