Implement critical fix for session handling and add centralized metadata structure

- Updated CourseLiveSessionRoomCreateAPIView to filter out ended sessions by adding `ended_at__isnull=True` in the session creation logic.
- Introduced a new method in CourseLiveSessionTokenAPIView to build centralized metadata for room settings, ensuring client overrides are not permitted and defining default lock settings and room features.

apps/course/views/live_session.py

@@ -97,8 +97,9 @@ class CourseLiveSessionRoomCreateAPIView(GenericAPIView):
             raise AppAPIException({'message': str(exc)}, status_code=500)
 
         # 5. Database Logic
+        # CRITICAL FIX: Also filter by ended_at__isnull=True to avoid reusing ended sessions
         session, created = CourseLiveSession.objects.get_or_create(
-            course=course, room_id=room_id,
+            course=course, room_id=room_id, ended_at__isnull=True,
             defaults={'subject': subject, 'started_at': timezone.now()}
         )
 
@@ -396,6 +397,59 @@ class CourseLiveSessionTokenAPIView(GenericAPIView):
             'plugnmeet': plugnmeet_response,
         })
 
+    def _build_metadata(self, subject: str) -> dict:
+        # Build secured, centralized metadata. Client overrides are NOT allowed.
+        return {
+            'room_title': subject,
+            'default_lock_settings': {
+                'lock_microphone': True,
+                'lock_webcam': True,
+                'lock_screen_sharing': True,
+                'lock_whiteboard': False,
+                'lock_shared_notepad': False,
+                'lock_chat': False,
+                'lock_chat_send_message': False,
+                'lock_chat_file_share': False,
+                'lock_private_chat': False,
+            },
+            'room_features': {
+                'allow_webcams': True,
+                'mute_on_start': True,
+                'allow_screen_sharing': True,
+                'allow_recording': True,
+                'allow_rtmp': False,
+                'allow_view_other_webcams': True,
+                'allow_view_other_participants_list': True,
+                'admin_only_webcams': False,
+                'allow_polls': True,
+                'room_duration': 0,
+                'chat_features': {
+                    'allow_chat': True,
+                    'allow_file_upload': True,
+                },
+                'shared_note_pad_features': {
+                    'allowed_shared_note_pad': True,
+                },
+                'whiteboard_features': {
+                    'allowed_whiteboard': True,
+                },
+                'breakout_room_features': {
+                    'is_allow': True,
+                    'allowed_number_rooms': 6,
+                },
+                'waiting_room_features': {
+                    'is_active': False,
+                },
+                'recording_features': {
+                    'is_allow': True,
+                    'is_allow_cloud': True,
+                    'is_allow_local': True,
+                    'enable_auto_cloud_recording': False,
+                    'only_record_admin_webcams': False,
+                },
+            },
+        }
+
     @staticmethod
     def _verify_room_is_active(session: CourseLiveSession) -> bool:
         """