feat: patch nextcloud-talk-desktop for Wayland screen sharing

Patches the Electron asar bundle to inject setDisplayMediaRequestHandler
with useSystemPicker: true, which routes screen capture through the
native PipeWire/xdg-desktop-portal pipeline on Wayland.

Based on upstream draft PR nextcloud/talk-desktop#1022.
Uses the patched version in communication role.

home/roles/communication/default.nix

@@ -20,7 +20,7 @@ in
       pkgs.element-desktop
       # Re-enabled in 25.11 after security issues were resolved
       pkgs.fluffychat
-      pkgs.nextcloud-talk-desktop
+      pkgs.custom.nextcloud-talk-desktop
     ];
   };
 }