Preserve entry.client.js in prod mode (#5813)

Author: masenf

reflex/compiler/compiler.py

@@ -621,7 +621,10 @@ def purge_web_pages_dir():
         return
 
     # Empty out the web pages directory.
-    utils.empty_dir(get_web_dir() / constants.Dirs.PAGES, keep_files=["routes.js"])
+    utils.empty_dir(
+        get_web_dir() / constants.Dirs.PAGES,
+        keep_files=["routes.js", "entry.client.js"],
+    )
 
 
 if TYPE_CHECKING: