fix(modules): improve module deduplication by using direct file refer…

…ence

Change module import from `import ./modules` to `./modules` to:
- Ensure proper _file attribute definition
- Enable correct module deduplication
- Improve error message clarity

This fixes issues with multiple imports of modules by letting Nix
automatically handle file path tracking and deduplication.

flake.nix

@@ -24,7 +24,7 @@
       flake = {
         homeManagerModules = {
           default = inputs.self.homeManagerModules.cosmic-manager;
-          cosmic-manager = import ./modules;
+          cosmic-manager = ./modules;
         };
       };