feat(themes): declaratively manage icons, cursors, and dark/light modes

- Automatically detect light mode via 'light.mode' file in theme folder
- Read icon theme name from 'icons.theme' file in theme folder
- Switch Stylix polarity and iconTheme based on theme selection
- Add yaru-theme and bibata-cursors to default packages
- Remove obsolete imperative nomarchy-theme-set-gnome script

modules/home/state.nix

@@ -117,6 +117,15 @@ in
         border_size = togglesState.hyprland.border_size or 2;
       };
       fonts.monospace = togglesState.font or "JetBrainsMono Nerd Font";
+      
+      # Derived properties from the theme directory
+      isLightMode = builtins.pathExists (../../themes + "/${togglesState.theme or "nord"}/light.mode");
+      iconsTheme = let
+        iconsFile = ../../themes + "/${togglesState.theme or "nord"}/icons.theme";
+      in
+        if builtins.pathExists iconsFile 
+        then lib.removeSuffix "\n" (builtins.readFile iconsFile)
+        else "Yaru-blue";
     };
   };
 }