feat(spa): add USE_SPA_UI cutover flag with legacy fallback

lobby/tests.py

@@ -5,7 +5,7 @@ from pathlib import Path
 
 from django.contrib.auth import get_user_model
 from django.core.management import call_command
-from django.test import TestCase
+from django.test import TestCase, override_settings
 from django.urls import reverse
 from django.utils import timezone
 
@@ -973,6 +973,38 @@ class UiScreenTests(TestCase):
         self.assertContains(response, "player_shell_runtime_error")
         self.assertContains(response, "window.addEventListener(\"error\"")
 
+    @override_settings(USE_SPA_UI=False)
+    def test_legacy_templates_are_used_when_spa_flag_is_off(self):
+        self.client.login(username="host_ui", password="secret123")
+
+        host_response = self.client.get(reverse("lobby:host_screen"))
+        player_response = self.client.get(reverse("lobby:player_screen"))
+
+        self.assertContains(host_response, "Host panel")
+        self.assertContains(player_response, "Player panel")
+        self.assertNotContains(host_response, "<app-root")
+        self.assertNotContains(player_response, "<app-root")
+
+    @override_settings(USE_SPA_UI=True)
+    def test_host_screen_can_render_angular_shell_when_feature_flag_enabled(self):
+        self.client.login(username="host_ui", password="secret123")
+
+        response = self.client.get(reverse("lobby:host_screen"))
+
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "<app-root")
+        self.assertContains(response, "data-wpp-shell-route=\"/host\"")
+        self.assertContains(response, "/static/frontend/angular/browser/main.js")
+
+    @override_settings(USE_SPA_UI=True)
+    def test_player_screen_can_render_angular_shell_when_feature_flag_enabled(self):
+        response = self.client.get(reverse("lobby:player_screen"))
+
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "<app-root")
+        self.assertContains(response, "data-wpp-shell-route=\"/player\"")
+        self.assertContains(response, "/static/frontend/angular/browser/main.js")
+
 
 class SessionDetailRoundQuestionTests(TestCase):
     def setUp(self):