nixos: change kernel from LTS to CachyOS-x86_64-v3-LTO

hosts/shared/nixos.nix

@@ -19,6 +19,9 @@ in
 
     consoleLogLevel = 3;
 
+    # Use latest LTO optimized x86_64-v3 kernel from CachyOS.
+    kernelPackages = pkgs.cachyosKernels.linuxPackages-cachyos-latest-lto-x86_64-v3;
+
     extraModulePackages = [ config.boot.kernelPackages.kvmfr ];
 
     kernelParams = [
@@ -257,8 +260,8 @@ in
   nixpkgs = {
     config.allowUnfree = true;
     overlays = [
-      # Disable temporarily as CDN is down for downloads causing build failures.
       inputs.affinity-nix.overlays.default
+      inputs.nix-cachyos-kernel.overlays.default
     ];
   };