Add consent dialog before EPLAN (.edz) import

Shows the licensing/liability warning text agreed on in PR #513
(scorpio810) before the file picker opens. Import stays disabled
until the "I have read and accept these terms" checkbox is ticked.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

sources/ElementsCollection/elementscollectionwidget.h

@@ -72,6 +72,7 @@ class ElementsCollectionWidget : public QWidget
 		void editDirectory();
 		void newDirectory();
 		void newElement();
+		bool confirmEdzImportTerms();
 		void importEdz();
 		void showThisDir();
 		void resetShowThisDir();