split the selection panel into one card per kind of selection

src/ui/selection/StationContent.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "entt/entity/entity.hpp"
+
+#include "SelectionContent.h"
+#include "SelectionContentFactory.h"
+
+class QLabel;
+
+// The card for one selected defence station, player or enemy
+// (REQ-UI-STATION-STATS-PANEL): its HP plus the combined damage, range and fire rate of
+// the weapon modules mounted on it.
+class StationContent : public SelectionContent
+{
+    Q_OBJECT
+
+public:
+    StationContent(const SelectionContext& context, const SelectionRequest& request,
+                   QWidget* parent = nullptr);
+
+protected:
+    void refreshRuntime() override;
+
+private:
+    entt::entity m_entity;
+    QLabel*      m_statsLabel;
+};