Use static self-registration for action queue and variable setup

Removes explicit setup calls from the plugin core. Each module now
registers its own save/load/cleanup steps via a static initializer,
decoupling them from InitSceneSwitcher and SwitcherData.

lib/queue/action-queue.hpp

@@ -101,7 +101,6 @@ signals:
 };
 
 std::deque<std::shared_ptr<Item>> &GetActionQueues();
-void SetupActionQueues();
 void SaveActionQueues(obs_data_t *);
 void LoadActionQueues(obs_data_t *);
 void ImportQueues(obs_data_t *);