Update test template to use create_app_fixture

Replaces the use of 'local_app' with 'app' and utilizes 'create_app_fixture' from shiny.pytest for test setup. This improves consistency and aligns with updated testing practices.

Author: karangattu

shiny/_main_add_test.py

@@ -85,12 +85,15 @@ def path_does_not_exist(x: Path) -> bool | str:
 from playwright.sync_api import Page
 
 from shiny.playwright import controller
+from shiny.pytest import create_app_fixture
 from shiny.run import ShinyAppProc
 
+app = create_app_fixture("{app_file.name}")
+
 
-def {test_name}(page: Page, local_app: ShinyAppProc):
+def {test_name}(page: Page, app: ShinyAppProc):
 
-    page.goto(local_app.url)
+    page.goto(app.url)
     # Add test code here
 """
         if is_same_dir