refactor: replace n8n package with overlay override

flake.nix

@@ -49,12 +49,13 @@
 
     # Overlays - can be imported in your system configuration
     overlays = {
-      # Default overlay: adds all custom packages
+      # Default overlay: adds all custom packages and applies package modifications.
       default = final: prev:
         import ./pkgs {
           pkgs = final;
           inputs = inputs;
-        };
+        }
+        // import ./overlays/mods {inherit prev;};
 
       modifications = final: prev: import ./overlays/mods {inherit prev;};
     };
@@ -104,6 +105,9 @@
           ${pkgs.alejandra}/bin/alejandra --check ${./.}
           touch $out
         '';
+        n8n-overlay = import ./tests/n8n-overlay-test.nix {
+          inherit pkgs inputs self;
+        };
         # Lib unit tests
         lib-agents = import ./tests/lib/agents-test.nix {
           inherit pkgs;