hypr: move session daemons from exec-once to systemd user services

Replace the hl.exec_cmd autostart block with declarative home-manager
services so the desktop shell has proper ordering and lifecycle:

- services.hyprpaper (with settings) for hyprpaper
- services.cliphist for the text/image clipboard watchers
- services.hyprpolkitagent for the polkit agent
- programs.quickshell.systemd for the quickshell shell
- a hand-written systemd.user.services.mako (home-manager has no unit)

All are tied to config.wayland.systemd.target (graphical-session.target),
which start-hyprland already activates. No UWSM required.

home/hypr/quickshell.nix

@@ -14,11 +14,6 @@ let
       (pkgs.quickshell or pkgs.qt6.qtbase);
 in
 {
-  home.packages = with pkgs; [
-    quickshellPkg
-    qt6.qtwayland
-  ];
-
   # Quickshell overview module for Hyprland (Super+Tab workspace overview).
   # Vendored from: https://github.com/Shanu-Kumawat/quickshell-overview
   # Placed at the quickshell config root so a bare `qs` finds shell.qml.
@@ -26,4 +21,15 @@ in
     source = ./quickshell;
     recursive = true;
   };
+
+  # Run quickshell as a systemd user service tied to the Wayland session.
+  programs.quickshell = {
+    enable = true;
+    package = quickshellPkg;
+    systemd.enable = true;
+  };
+
+  home.packages = with pkgs; [
+    qt6.qtwayland
+  ];
 }