feat(specialists): owner is non-deletable specialist on commercial create

Bootstrap calendar_specialist for owner (active); DELETE owner → 403;
toggle via status. Fixes solo assign-to-slot. Refs EventHub/EventHubBack#66

test/unit/logic_calendar_tests.erl

@@ -16,9 +16,14 @@ setup() ->
     {attributes, record_info(fields, subscription)},
     {ram_copies, [node()]}
   ]),
+  mnesia:create_table(calendar_specialist, [
+    {attributes, record_info(fields, calendar_specialist)},
+    {ram_copies, [node()]}
+  ]),
   ok.
 
 cleanup(_) ->
+  mnesia:delete_table(calendar_specialist),
   mnesia:delete_table(subscription),
   mnesia:delete_table(calendar),
   mnesia:delete_table(user),