do not reload compilation if using local app in AppHarness (#3790)

* do not reload if using local app

* Update reflex/testing.py

Co-authored-by: Masen Furer <m_github@0x26.net>

---------

Co-authored-by: Masen Furer <m_github@0x26.net>

reflex/testing.py

@@ -276,7 +276,10 @@ def _initialize_app(self):
             before_decorated_pages = reflex.app.DECORATED_PAGES[self.app_name].copy()
             # Ensure the AppHarness test does not skip State assignment due to running via pytest
             os.environ.pop(reflex.constants.PYTEST_CURRENT_TEST, None)
-            self.app_module = reflex.utils.prerequisites.get_compiled_app(reload=True)
+            self.app_module = reflex.utils.prerequisites.get_compiled_app(
+                # Do not reload the module for pre-existing apps (only apps generated from source)
+                reload=self.app_source is not None
+            )
             # Save the pages that were added during testing
             self._decorated_pages = [
                 p