Add DMS configuration enhancements and new default settings

- Introduced a new private default settings file for Dank Material Shell (DMS) to manage user-specific settings.
- Updated DMS home-manager module to generate a settings seed file, merging extra right-bar widgets into the first-run configuration.
- Added support for dynamic inclusion of DMS window rules based on user configuration.
- Enhanced the Niri configuration with a preference for no client-side decorations and improved keybindings for bar toggling.

modules/desktop/shells/dms/default.nix

@@ -24,7 +24,7 @@
       extraRightBarWidgets = lib.mkOption {
         type = lib.types.listOf lib.types.attrs;
         default = [ ];
-        description = "Extra right-bar widgets (prepended).";
+        description = "Extra right-bar widgets merged into the first-run DMS settings seed.";
       };
       enableWvkbdToggle = lib.mkEnableOption ''
         wvkbd DMS plugin + bar toggle (touch / uConsole).