Add Losslesscut AppImage and update host configs

Enable the Losslesscut AppImage on the Garand‑Desktop host
while keeping it disabled on the laptop and default hosts.

Add opencode to the laptop home configuration
and explicitly disable ollama.

Add a new losslesscut AppImage package definition
and register it in the AppImage collection.

Extend the substituter list with noctalia.cachix.org
and add its trusted public key.

modules/core/packages/appimages/default.nix

@@ -14,6 +14,7 @@
   appImagePackages = {
     fluxer = pkgs.callPackage ./fluxer.nix {};
     helium = pkgs.callPackage ./helium.nix {};
+    losslesscut = pkgs.callPackage ./losslesscut.nix {};
   };
 in {
   imports = builtins.attrValues (builtins.mapAttrs mkAppImagePackage appImagePackages);