fix: Unset PATH that is auto-generated by Nix

This addresses a problem where the launcher is
not able to actually launch any applications when
it is started by a systemd unit generated by Nix.

The search path would typically be inherited by a
systemd unit, but Nix's unit generator will
assign a specific, minimal PATH that only includes
the unit's runtime dependencies.

flake.nix

@@ -266,6 +266,10 @@
               wantedBy = [ cfg.target ];
               restartTriggers = [ cfg.package ];
 
+              environment = {
+                PATH = lib.mkForce null;
+              };
+
               unitConfig = {
                 StartLimitIntervalSec = 60;
                 StartLimitBurst = 3;
@@ -278,7 +282,6 @@
                 TimeoutStartSec = 10;
                 TimeoutStopSec = 5;
                 Environment = [
-                  "PATH=${config.system.path}/bin"
                   "NOCTALIA_SETTINGS_FALLBACK=%h/.config/noctalia/gui-settings.json"
                 ];
               };