cli: always use main entry point in packages for backend development

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/spotty-swans-run.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+The backend development setup now ignores the `"browser"` and `"module"` entry points in `package.json`, and instead always uses `"main"`.

packages/cli/src/lib/bundler/config.ts

@@ -272,7 +272,7 @@ export async function createBackendConfig(
     ],
     resolve: {
       extensions: ['.ts', '.tsx', '.mjs', '.js', '.jsx'],
-      mainFields: ['browser', 'module', 'main'],
+      mainFields: ['main'],
       modules: [paths.rootNodeModules, ...moduleDirs],
       plugins: [
         new LinkedPackageResolvePlugin(paths.rootNodeModules, externalPkgs),