fix: spec review - add missing fish module to base/shell

- Create home/base/shell/fish.nix
- Add to base/shell/default.nix imports
- Migrate remaining hosts from features.cli.fish to base.shell.fish

home/m3tam3re/m3-helios.nix

@@ -13,13 +13,12 @@ in {
       context = "server";
     })
     ./home-server.nix
-    # Fish shell — no equivalent in new base module yet
-    ../features/cli/fish.nix
   ];
 
   # Base CLI tools (new namespace)
   base = {
     shell = {
+      fish.enable = true;
       starship.enable = true;
     };
     cliTools = {
@@ -28,6 +27,4 @@ in {
     };
   };
 
-  # Fish shell (legacy — no new equivalent yet)
-  features.cli.fish.enable = true;
 }