feat(materials): show save progress overlay while optimizing images

Block the editor with a spinner and percent stages during material upsert so long image optimization is visible and non-interactive.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/editor/i18n/editorMessages.ts

@@ -365,6 +365,9 @@ export const EDITOR_MESSAGES: Record<EditorLocale, Record<string, string>> = {
     'materials.add': 'Добавить',
     'materials.addTitle': 'Новый материал',
     'materials.editTitle': 'Изменить материал',
+    'materials.savingTitle': 'Сохранение материала',
+    'materials.savingWait': 'Подождите…',
+    'materials.savingProgress': 'Прогресс сохранения материала',
     'materials.edit': 'Изменить',
     'materials.search': 'Поиск материалов…',
     'materials.searchEmpty': 'Ничего не найдено.',
@@ -912,6 +915,9 @@ export const EDITOR_MESSAGES: Record<EditorLocale, Record<string, string>> = {
     'materials.add': 'Add',
     'materials.addTitle': 'New material',
     'materials.editTitle': 'Edit material',
+    'materials.savingTitle': 'Saving material',
+    'materials.savingWait': 'Please wait…',
+    'materials.savingProgress': 'Material save progress',
     'materials.edit': 'Edit',
     'materials.search': 'Search materials…',
     'materials.searchEmpty': 'No matches.',