feat(project): optimize image imports and converter

- Optimize imported scene preview images (smart WebP/JPEG/PNG, preserve alpha, keep pixel size)

- Update converter to re-encode existing image assets with same algorithm

- Improve import/export progress overlay and reduce presentation slide stutter

Made-with: Cursor

app/main/index.ts

@@ -27,6 +27,20 @@ import {
   waitForEditorWindowReady,
 } from './windows/createWindows';
 
+function emitZipProgress(evt: {
+  kind: 'import' | 'export';
+  stage: string;
+  percent: number;
+  detail?: string;
+}): void {
+  for (const win of BrowserWindow.getAllWindows()) {
+    win.webContents.send(
+      evt.kind === 'import' ? ipcChannels.project.importZipProgress : ipcChannels.project.exportZipProgress,
+      evt,
+    );
+  }
+}
+
 /**
  * Отключение GPU ломает скорость вторичных окон (презентация/пульт — WebGL). По умолчанию не трогаем.
  * При чёрном экране в упакованной сборке: `DND_DISABLE_GPU=1`.
@@ -403,7 +417,18 @@ async function main() {
     if (canceled || !filePaths[0]) {
       return { canceled: true as const };
     }
-    const project = await projectStore.importProjectFromExternalZip(filePaths[0]);
+    const srcPath = filePaths[0];
+    emitZipProgress({ kind: 'import', stage: 'copy', percent: 0, detail: 'Копирование…' });
+    // Let store import; progress for unzip is emitted from unzipToDir wrapper in store.
+    const project = await projectStore.importProjectFromExternalZip(srcPath, (p) => {
+      emitZipProgress({
+        kind: 'import',
+        stage: p.stage,
+        percent: p.percent,
+        ...(p.detail ? { detail: p.detail } : null),
+      });
+    });
+    emitZipProgress({ kind: 'import', stage: 'done', percent: 100, detail: 'Готово' });
     emitSessionState();
     return { canceled: false as const, project };
   });
@@ -428,7 +453,16 @@ async function main() {
     if (!lower.endsWith('.dnd.zip')) {
       dest = lower.endsWith('.zip') ? dest.replace(/\.zip$/iu, '.dnd.zip') : `${dest}.dnd.zip`;
     }
-    await projectStore.exportProjectZipToPath(projectId, dest);
+    emitZipProgress({ kind: 'export', stage: 'copy', percent: 0, detail: 'Экспорт…' });
+    await projectStore.exportProjectZipToPath(projectId, dest, (p) => {
+      emitZipProgress({
+        kind: 'export',
+        stage: p.stage,
+        percent: p.percent,
+        ...(p.detail ? { detail: p.detail } : null),
+      });
+    });
+    emitZipProgress({ kind: 'export', stage: 'done', percent: 100, detail: 'Готово' });
     return { canceled: false as const };
   });
   registerHandler(ipcChannels.project.deleteProject, async ({ projectId }) => {