fix: preserve better-auth exports in dist package.json

The postprocess-files.cjs was replacing all exports with auto-generated
ones, losing the custom better-auth subpath exports needed for:
- inboundemail/better-auth
- inboundemail/better-auth/client
- inboundemail/better-auth/react-email

Author: R44VC0RP

scripts/utils/postprocess-files.cjs

@@ -44,6 +44,19 @@ async function postprocess() {
       types: './index.d.mts',
       default: './index.mjs',
     },
+    // Better Auth integration exports
+    './better-auth': {
+      import: './integrations/better-auth/index.mjs',
+      require: './integrations/better-auth/index.js',
+    },
+    './better-auth/client': {
+      import: './integrations/better-auth/client.mjs',
+      require: './integrations/better-auth/client.js',
+    },
+    './better-auth/react-email': {
+      import: './integrations/better-auth/react-email/index.mjs',
+      require: './integrations/better-auth/react-email/index.js',
+    },
   };
 
   for (const entry of await fs.promises.readdir(distDir, { withFileTypes: true })) {