refactor: make shared_qobject_ptr ctor explicit

This turns issues like creating two shared ptrs from a single raw ptr
from popping up at runtime, instead making them a compile error.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/tasks/ConcurrentTask.h

@@ -8,6 +8,8 @@
 class ConcurrentTask : public Task {
     Q_OBJECT
 public:
+    using Ptr = shared_qobject_ptr<ConcurrentTask>;
+
     explicit ConcurrentTask(QObject* parent = nullptr, QString task_name = "", int max_concurrent = 6);
     ~ConcurrentTask() override;