fix(events): guard booking_occupancy when booking table missing

Admin eunit suites call event_to_json without Mnesia booking table;
catch list_by_event failures and treat as free.

src/handlers/handler_utils.erl

@@ -345,9 +345,16 @@ event_to_json(Event) ->
   }.
 
 %% @doc Активная занятость слота для сетки commercial (Studio aggregate).
+%% Safe if Mnesia booking table is not ready (admin/unit tests without full schema).
 -spec booking_occupancy(#event{}) -> free | pending | confirmed.
 booking_occupancy(#event{id = EventId, start_time = Start}) ->
-  {ok, Bookings} = core_booking:list_by_event(EventId),
+  Bookings =
+    try
+      {ok, List} = core_booking:list_by_event(EventId),
+      List
+    catch
+      _:_ -> []
+    end,
   Now = calendar:universal_time(),
   lists:foldl(
     fun(#booking{status = confirmed}, _Acc) ->