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/project/yauzlProjectZip.ts

@@ -5,12 +5,18 @@ import yauzl from 'yauzl';
 
 import type { Project } from '../../shared/types';
 
-export function unzipToDir(zipPath: string, outDir: string): Promise<void> {
+export function unzipToDir(
+  zipPath: string,
+  outDir: string,
+  onProgress?: (done: number, total: number) => void,
+): Promise<void> {
   return new Promise((resolve, reject) => {
     yauzl.open(zipPath, { lazyEntries: true }, (err, zip) => {
       if (err) return reject(err);
       const zipFile = zip;
       let settled = false;
+      const total = zipFile.entryCount || 0;
+      let done = 0;
 
       const safeClose = (): void => {
         try {
@@ -37,6 +43,14 @@ export function unzipToDir(zipPath: string, outDir: string): Promise<void> {
       zipFile.readEntry();
       zipFile.on('entry', (entry: yauzl.Entry) => {
         if (settled) return;
+        done += 1;
+        if (onProgress && total > 0) {
+          try {
+            onProgress(done, total);
+          } catch {
+            // ignore
+          }
+        }
         const filePath = path.join(outDir, entry.fileName);
         if (entry.fileName.endsWith('/')) {
           fssync.mkdirSync(filePath, { recursive: true });