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

tools/project-converter/package.json

@@ -0,0 +1,21 @@
+{
+  "name": "dnd-project-converter",
+  "private": true,
+  "version": "0.1.0",
+  "description": "Simple UI tool to convert .dnd.zip projects (add scene preview thumbnails).",
+  "type": "module",
+  "main": "src/main.js",
+  "scripts": {
+    "dev": "node src/run-electron.mjs",
+    "start": "node src/run-electron.mjs",
+    "lint": "node -e \"console.log('no lint')\""
+  },
+  "dependencies": {
+    "electron": "^41.2.0",
+    "ffmpeg-static": "^5.3.0",
+    "sharp": "^0.34.5",
+    "yauzl": "^3.3.0",
+    "yazl": "^3.3.1"
+  }
+}
+