manatee: Add services homepage with auto-discovery

Add a homepage module that generates a static landing page served on
port 80 via nginx. Each service module registers itself via the shared
mod.homepage.services option, so enabling a module automatically adds
it to the page.

hosts/manatee/modules/default.nix

@@ -22,6 +22,7 @@ in
       immich.enable = true;
       navidrome.enable = true;
       komga.enable = true;
+      homepage.enable = true;
     };
   };
 }