Exclude bun.lockb from omnix text substitution

Prevents "stream did not contain valid UTF-8" errors during template
initialization. The binary lockfile doesn't need text substitution and
should be copied as-is.

nix/modules/template.nix

@@ -24,6 +24,7 @@ in {
             placeholder = "my-project";
           }
         ];
+        exclude = ["bun.lockb"];
       };
 
       javascript-nextjs = {
@@ -35,6 +36,7 @@ in {
             placeholder = "my-nextjs-app";
           }
         ];
+        exclude = ["bun.lockb"];
       };
     };
   };