data: Save timestamp of project indexing and show it in overview

src/lib/data/PersistentStorage.cpp

@@ -559,6 +559,7 @@ void PersistentStorage::optimizeMemory()
 	TRACE();
 
 	m_sqliteIndexStorage.setVersion();
+	m_sqliteIndexStorage.setTime();
 	m_sqliteIndexStorage.optimizeMemory();
 
 	m_sqliteBookmarkStorage.setVersion();
@@ -1411,6 +1412,8 @@ StorageStats PersistentStorage::getStorageStats() const
 	stats.completedFileCount = m_sqliteIndexStorage.getCompletedFileCount();
 	stats.fileLOCCount = m_sqliteIndexStorage.getFileLineSum();
 
+	stats.timestamp = m_sqliteIndexStorage.getTime();
+
 	return stats;
 }