Add Qt-only autosave recovery fallback

Provide a small KAutoSaveFile-compatible implementation for the no-KF5 build path and use it to keep the existing crash-recovery code active when BUILD_WITH_KF5=OFF.

The normal KF5 build still uses the KDE KAutoSaveFile implementation.

Assisted-by: pi coding agent / Mika (OpenAI GPT-5.5)

sources/ui/nokde/kautosavefile.h

@@ -0,0 +1,61 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#ifndef QET_KAUTOSAVEFILE_H
+#define QET_KAUTOSAVEFILE_H
+
+#include <QFile>
+#include <QList>
+#include <QUrl>
+
+#include <memory>
+
+class QLockFile;
+
+/**
+	Small Qt-only replacement for the KAutoSaveFile API used by QET.
+
+	It stores crash-recovery files below the application data autosave folder
+	and protects each recovery file with QLockFile.  The original managed file
+	path is kept in a sidecar file so allStaleFiles() can present recoverable
+	projects on the next startup.
+*/
+class KAutoSaveFile : public QFile
+{
+	public:
+		explicit KAutoSaveFile(const QUrl &filename, QObject *parent = nullptr);
+		explicit KAutoSaveFile(QObject *parent = nullptr);
+		~KAutoSaveFile() override;
+
+		QUrl managedFile() const;
+		void setManagedFile(const QUrl &filename);
+		virtual void releaseLock();
+		bool open(OpenMode openmode) override;
+
+		static QList<KAutoSaveFile *> staleFiles(
+			const QUrl &url,
+			const QString &applicationName = QString());
+		static QList<KAutoSaveFile *> allStaleFiles(
+			const QString &applicationName = QString());
+
+	private:
+		QUrl m_managed_file;
+		std::unique_ptr<QLockFile> m_lock;
+		bool m_managed_file_name_changed = false;
+};
+
+#endif // QET_KAUTOSAVEFILE_H