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/renderer/editor/EditorApp.module.css

@@ -124,6 +124,52 @@
   background: var(--bg0);
 }
 
+.progressOverlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.55);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 10000;
+}
+
+.progressModal {
+  width: min(520px, calc(100vw - 32px));
+  border-radius: 12px;
+  padding: 14px;
+  background: rgba(25, 28, 38, 0.92);
+  border: 1px solid rgba(255, 255, 255, 0.12);
+  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.55);
+}
+
+.progressTitle {
+  font-weight: 700;
+  margin-bottom: 10px;
+}
+
+.progressBar {
+  height: 10px;
+  border-radius: 999px;
+  overflow: hidden;
+  background: rgba(255, 255, 255, 0.08);
+  border: 1px solid rgba(255, 255, 255, 0.1);
+}
+
+.progressFill {
+  height: 100%;
+  width: 0%;
+  background: rgba(167, 139, 250, 0.85);
+}
+
+.progressMeta {
+  margin-top: 10px;
+  display: flex;
+  justify-content: space-between;
+  opacity: 0.9;
+  font-size: 12px;
+}
+
 .inspectorTitle {
   font-weight: 800;
   margin-bottom: 12px;