chore: update nix dev shells and pnpm build settings

backend/shell.nix

@@ -10,6 +10,7 @@ pkgs.mkShell {
     # postgres database
     postgresql
 
+    claude-code
   ];
 
   shellHook = ''

frontend/pnpm-workspace.yaml

@@ -1,3 +1,7 @@
+allowBuilds:
+  core-js: true
+  es5-ext: true
+  esbuild: true
 onlyBuiltDependencies:
   - esbuild
   - '@tailwindcss/oxide'

frontend/shell.nix

@@ -4,7 +4,8 @@ pkgs.mkShell {
   buildInputs = with pkgs; [
     # Node.js ecosystem
     nodejs_24
-    nodePackages.pnpm
+    pnpm
+    claude-code
   ];
 
   shellHook = ''