✨(backend) add minimal Recording viewset for room recordings

Implements routes to manage recordings within rooms, following the patterns
established in Impress. The viewset exposes targeted endpoints rather than
full CRUD operations, with recordings being created (soon) through
room-specific routes (e.g. room/123/start-recording).

The implementation draws from @sampaccoud's initial work and advices.

Review focus areas:
- Permission implementation choices
- Serializer design and structure

Credit: Initial work by @sampaccoud

src/backend/core/api/serializers.py

@@ -87,6 +87,15 @@ class NestedResourceAccessSerializer(ResourceAccessSerializer):
     user = UserSerializer(read_only=True)
 
 
+class ListRoomSerializer(serializers.ModelSerializer):
+    """Serialize Room model for a list API endpoint."""
+
+    class Meta:
+        model = models.Room
+        fields = ["id", "name", "slug", "is_public"]
+        read_only_fields = ["id", "slug"]
+
+
 class RoomSerializer(serializers.ModelSerializer):
     """Serialize Room model for the API."""
 
@@ -136,3 +145,14 @@ class RoomSerializer(serializers.ModelSerializer):
         output["is_administrable"] = is_admin
 
         return output
+
+
+class RecordingSerializer(serializers.ModelSerializer):
+    """Serialize Recording for the API."""
+
+    room = ListRoomSerializer(read_only=True)
+
+    class Meta:
+        model = models.Recording
+        fields = ["id", "room", "created_at", "updated_at", "status"]
+        read_only_fields = fields